Content uploaded by John Westbrook
Author content
All content in this area was uploaded by John Westbrook on Jan 06, 2014
Content may be subject to copyright.
© 2000 Oxford University Press Nucleic Acids Research, 2000, Vol. 28, No. 1 235–242
The Protein Data Bank
Helen M. Berman
1,2,
*, John Westbrook
1,2
, Zukang Feng
1,2
, Gary Gilliland
1,3
,T.N.Bhat
1,3
,
Helge Weissig
1,4
, Ilya N. Shindyalov
4
and Philip E. Bourne
1,4,5,6
1
Research Collaboratory for Structural Bioinformatics (RCSB),
2
Department of Chemistry, Rutgers University,
610 Taylor Road, Piscataway, NJ 08854-8087, USA,
3
National Institute of Standards and Technology, Route 270,
Quince Orchard Road, Gaithersburg, MD 20899, USA,
4
San Diego Supercomputer Center, University of California,
San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0505, USA,
5
Department of Pharmacology,
University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0500, USA and
6
The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
Received September 20, 1999; Revised and Accepted October 17, 1999
ABSTRACT
The Protein Data Bank (PDB; http://www.rcsb.org/pdb/ )
is the single worldwide archive of structural data of
biological macromolecules. This paper describes the
goals of the PDB, the systems in place for data depo-
sition and access, how to obtain further information,
and near-term plansfor the future development of the
resource.
INTRODUCTION
The Protein Data Bank (PDB) was established at Brookhaven
National Laboratories (BNL) (1) in 1971 as an archive for
biological macromolecular crystal structures. In the beginning
the archive held seven structures, and with each year a handful
more were deposited. In the 1980s the number of deposited
structures began to increase dramatically. This was due to the
improved technology for all aspects of the crystallographic
process, the addition of structures determined by nuclear
magnetic resonance (NMR) methods, and changes in the
community views about data sharing. By the early 1990s the
majority of journals required a PDB accession code and at least
one funding agency (National Institute of General Medical
Sciences) adopted the guidelines published by the International
Union of Crystallography (IUCr) requiring data deposition for
all structures.
The mode of access to PDB data has changed over the years
as a result of improved technology, notably the availability of
the WWW replacing distribution solely via magnetic media.
Further, the need to analyze diverse data sets required the
development of modern data management systems.
Initial use of the PDB had been limited to a small group of
experts involved in structural research. Today depositors to the
PDB have varying expertise in the techniques of X-ray crystal
structure determination, NMR, cryoelectron microscopy and
theoretical modeling. Users are a very diverse group of
researchers in biology, chemistry and computer scientists,
educators, and students at all levels. The tremendous influx of
data soon to be fueled by the structural genomics initiative, and
the increased recognition of the value of the data toward
understanding biological function, demand new ways to
collect, organize and distribute the data.
In October 1998, the management of the PDB became the
responsibility of the Research Collaboratory for Structural
Bioinformatics (RCSB). In general terms, the vision of the
RCSB is to create a resource based on the most modern
technology that facilitates the use and analysis of structural
data and thus creates an enabling resource for biological
research. Specifically in this paper, we describe the current
procedures for data deposition, data processing and data
distribution of PDB data by the RCSB. In addition, we address
the issues of data uniformity. We conclude with some current
developments of the PDB.
DATA ACQUISITION AND PROCESSING
A key component of creating the public archive of information
is the efficient capture and curation of the data—data processing.
Data processing consists of data deposition, annotation and
validation. These steps are part of the fully documented and
integrated data processing system shown in Figure 1.
In the present system (Fig. 2), data (atomic coordinates,
structure factors and NMR restraints) may be submitted via
email or via the AutoDep Input Tool (ADIT; http://pdb.rutgers.
edu/adit/ ) developed by the RCSB. ADIT, which is also used
to process the entries, is built on top of the mmCIF dictionary
which is an ontology of 1700 terms that define the macro-
molecular structure and the crystallographic experiment (2,3),
and a data processing program called MAXIT (MAcromolecular
EXchange Input Tool). This integrated system helps to ensure
that the data submitted are consistent with the mmCIF
dictionary which defines data types, enumerates ranges of
allowable values where possible and describes allowable
relationships between data values.
After a structure has been deposited using ADIT, a PDB
identifier is sent to the author automatically and immediately
(Fig. 1, Step 1). This is the first stage in which information
about the structure is loaded into the internal core database (see
section on the PDB Database Resource). The entry is then
annotated as described in the validation section below. This
process involves using ADIT to help diagnose errors or
*To whom correspondence should be addressed at: Department of Chemistry, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854-8087, USA.
Tel: +1 732 445 4667; Fax: +1 732 445 4320; Email: berman@rcsb.rutgers.edu
236 Nucleic Acids Research, 2000, Vol. 28, No. 1
inconsistencies in the files. The completely annotated entry as
it will appear in the PDB resource, together with the validation
information, is sent back to the depositor (Step 2). After
reviewing the processed file, the author sends any revisions
(Step 3). Depending on the nature of these revisions, Steps 2
and 3 may be repeated. Once approval is received from the
author (Step 4), the entry and the tables in the internal core
database are ready for distribution. The schema of this core
database is a subset of the conceptual schema specified by the
mmCIF dictionary.
All aspects of data processing, including communications
with the author, are recorded and stored in the correspondence
archive. This makes it possible for the PDB staff to retrieve
information about any aspect of the deposition process and to
closely monitor the efficiency of PDB operations.
Current status information, comprised of a list of authors,
title and release category, is stored for each entry in the core
database and is made accessible for query via the WWW interface
(http://www.rcsb.org/pdb/status.html ). Entries before release
are categorized as ‘in processing’ (PROC), ‘in depositor
review’ (WAIT), ‘to be held until publication’ (HPUB) or ‘on
hold until a depositor-specified date’ (HOLD).
Content of the data collected by the PDB
All the data collected from depositors by the PDB are considered
primary data. Primary data contain, in addition to the coordinates,
general information required for all deposited structures and
information specific to the method of structure determination.
Table 1 contains the general information that the PDB collects
for all structures as wellas the additional information collected for
those structures determined by X-ray methods. The additional
items listed for the NMR structures are derived from the
International Union of Pure and Applied Chemistry recommen-
dations (IUPAC) (4) and will be implemented in the near future.
The information content of data submittedby the depositoris
likely to change as new methods for data collection, structure
determination and refinement evolve and advance. In addition,
the ways in which these data are captured are likely to change
as the software for structure determination and refinement
produce the necessary data items as part of their output. ADIT,
Figure 1. The steps in PDB data processing. Ellipses represent actions and rectangles define content.
Figure 2. The integrated tools of the PDB data processing system.
Table 1. Content of data in the PDB
Nucleic Acids Research, 2000, Vol. 28, No. 1 237
the data input system for the PDB, has been designed so as to
easily incorporate these likely changes.
Validation
Validation refers to the procedure for assessing the quality of
deposited atomic models (structure validation) and for
assessing how well these models fit the experimental data
(experimental validation). The PDB validates structures using
accepted community standards as part of ADIT’s integrated
data processing system. The following checks are run and are
summarized in a letter that is communicated directly to the
depositor:
Covalent bond distances and angles. Proteins are compared
against standard values from Engh and Huber (5); nucleic acid
bases are compared against standard values from Clowney
et al. (6); sugar and phosphates are compared against standard
values from Gelbin et al. (7).
Stereochemical validation. All chiral centers of proteins and
nucleic acids are checked for correct stereochemistry.
Atom nomenclature. The nomenclature of all atoms is checked
for compliance with IUPAC standards (8) and is adjusted if
necessary.
Close contacts. The distances between all atoms within the
asymmetric unit of crystal structures and the unique molecule
of NMR structures are calculated. For crystal structures,
contacts between symmetry-related molecules are checked as
well.
Ligand and atom nomenclature. Residue and atom nomen-
clature is compared against the PDB dictionary (ftp://ftp.rcsb.
org/pub/pdb/data/monomers/het_dictionary.txt ) for all ligands
as well as standard residues and bases. Unrecognized ligand
groups are flagged and any discrepancies in known ligands are
listed as extra or missing atoms.
Sequence comparison. The sequence given in the PDB SEQRES
records is compared against the sequence derived from the
coordinate records. This information is displayed in a table
where any differences or missing residues are marked. During
structure processing, the sequence database references given
by DBREF and SEQADV are checked for accuracy. If no
reference is given, a BLAST (9) search is used to find the best
match. Any conflict between the PDB SEQRES records and
the sequence derived from the coordinate records is resolved
by comparison with various sequence databases.
Distant waters. The distances between all water oxygen atoms
and all polar atoms (oxygen and nitrogen) of the macromolecules,
ligands and solvent in the asymmetric unit are calculated.
Distant solvent atoms are repositioned using crystallographic
symmetry such that they fall within the solvation sphere of the
macromolecule.
In almost all cases, serious errors detected by these checks are
corrected through annotation and correspondence with the authors.
It is also possible to run these validation checks against
structures before they are deposited. A validation server
(http://pdb.rutgers.edu/validate/ ) has been made available for
this purpose. In addition to the summary report letter, the
server also provides output from PROCHECK (10), NUCheck
(Rutgers University, 1998) and SFCHECK (11). A summary
atlas page and molecular graphics are also produced.
The PDB will continually review the checking methods used
and will integrate new procedures as they are developed by the
PDB and members of the scientific community.
Other data deposition centers
The PDB is working with other groups to set up deposition
centers. This enables people at other sites to more easily
deposit their data via the Internet. Because it is critical that the
final archive is kept uniform, the content and format of the
final files as well as the methods used to check them must be
the same. At present, the European Bioinformatics Institute
(EBI) processes data that are submitted to them via AutoDep
(http://autodep.ebi.ac.uk/ ). Once these data are processed they
are sent to the RCSB in PDB format for inclusion in the central
archive. Before this system was put in place it was tested to
ensure consistency among entries in the PDB archive. In the
future, the data will be exchanged in mmCIF format using a
common exchange dictionary, which along with standardized
annotation procedures will ensure a high degree of uniformity
in the archival data. Structures deposited and processed at the
EBI represent ~20% of all data deposited.
Data deposition will also soon be available from an ADIT
Web site at The Institute for Protein Research at Osaka
University in Japan. At first, structures deposited at this site
will be processed by the PDB staff. In time, the staff at Osaka
will complete the data processing for these entries and send the
files to the PDB for release.
NMR data
The PDB staff recognizes that NMR data needs a special
development effort. Historically these data have been retro-
fitted into a PDB format defined around crystallographic infor-
mation. As a first step towards improving this situation, the
PDB did an extensive assessment of the current NMR holdings
and presented their findings to a Task Force consisting of a
cross section of NMR researchers. The PDB is working with
this group, the BioMagResBank (BMRB) (12), as well as other
members of the NMR community, to develop an NMR data
dictionary along with deposition and validation tools specific
for NMR structures. This dictionary contains among other
items descriptions of the solution components, the experimental
conditions, enumerated lists of the instruments used, as well as
information about structure refinement.
Data processing statistics
Production processing of PDB entries by the RCSB began on
January 27, 1999. The median time from deposition to the
completion of data processing including author interactions is
less than 10 days. The number of structures with a HOLD
release status remains at ~22% of all submissions; 28% are
held until publication; and 50% are released immediately after
processing.
When the RCSB became fully responsible there were about
900 structures that had not been completely processed. These
included so called Layer 1 structures that had been processed
by computer software but had not been fully annotated. All of
238 Nucleic Acids Research, 2000, Vol. 28, No. 1
these structures have now been processed and are being
released after author review.
The breakdown of the types of structures in the PDB is
shown in Table 2. As of September 14, 1999, the PDB
contained 10 714 publicly accessible structures with another
1169 entries on hold. Of these, 8789 (82%) were determined
by X-ray methods, 1692 (16%) were determined by NMR and
233 (2%) were theoretical models. Overall, 35% of the entries
have deposited experimental data.
Data uniformity
A key goal of the PDB is to make the archive as consistent and
error-free as possible. All current depositions are reviewed
carefully by the staff before release. Tables of features are
generated from the internal data processing database and
checked. Errors found subsequent to release by authors and
PDB users are addressed as rapidly as possible. Corrections
and updates to entries should be sent to deposit@rcsb.
rutgers.edu for the changes to be implemented and re-released
into the PDB archive.
One of the most difficult problems that the PDB now faces is
that the legacy files are not uniform. Historically, existing data
(‘legacy data’) comply with several different PDB formats and
variation exists in how the same features are described for
different structures within each format. The introduction of the
advanced querying capabilities of the PDB makes it critical to
accelerate the data uniformity process for these data. We are
now at a stage where the query capabilities surpass the quality
of the underlying data. The data uniformity project is being
approached in two ways. Families of individual structures are
being reprocessed using ADIT. The strategy of processing data
files as groups of similar structures facilitates the application
of biological knowledge by the annotators. In addition, we are
examining particular records across all entries in the archive.
As an example, we have recently completed examining and
correcting the chemical descriptions of all of the ligands in the
PDB. These corrections are being entered in the database. The
practical consequence of this is that soon it will be possible to
accurately find all the structures in the PDB bound to a particular
ligand or ligand type. In addition to the efforts of the PDB to
remediate the older entries, the EBI has also corrected many of
the records in the PDB as part of their ‘clean-up’ project. The
task of integrating all of these corrections done at both sites is
very large and it is essential that there is a well-defined
exchange format to do this; mmCIF will be used for this
purpose.
THE PDB DATABASE RESOURCE
The database architecture
In recognition of the fact that no single architecture can fully
express and efficiently make available the information content
of the PDB, an integrated system of heterogeneous databases
has been created that store and organize the structural data. At
present there are five major components (Fig. 3):
• The core relational database managed by Sybase (Sybase
SQL server release 11.0, Emeryville, CA) provides the
central physical storage for the primary experimental and
coordinate data described in Table 1. The core PDB relational
database contains all deposited information in a tabular form
that can be accessed across any number of structures.
Table 2. Demographics of data in the PDB
Figure 3. The integrated query interface to the PDB.
Nucleic Acids Research, 2000, Vol. 28, No. 1 239
• The final curated data files (in PDB and mmCIF formats)
and data dictionaries are the archival data and are present as
ASCII files in the ftp archive.
• The POM (Property Object Model)-based databases, which
consist of indexed objects containing native (e.g., atomic
coordinates) and derived properties (e.g., calculated secondary
structure assignments and property profiles). Some properties
require no derivation, for example, B factors; others must be
derived, for example, exposure of each amino acid residue
(13) or C
contact maps. Properties requiring significant
computation time, such as structure neighbors (14), are pre-
calculated when the database is incremented to save considerable
user access time.
• The Biological Macromolecule Crystallization Database
(BMCD; 15) is organized as a relational database within
Sybase and contains three general categories of literature
derived information: macromolecular, crystal and summary
data.
• The Netscape LDAP server is used to index the textual
content of the PDB in a structured format and provides
support for keyword searches.
It is critical that the intricacies of the underlying physical
databases be transparent to the user. In the current implementation,
communication among databases has been accomplished using
the Common Gateway Interface (CGI). An integrated Web
interface dispatches a query to the appropriate database(s),
which then execute the query. Each database returns the PDB
identifiers that satisfy the query, and the CGI program integrates
the results. Complex queries are performed by repeating the
process and having the interface program perform the appropriate
Boolean operation(s) on the collection of query results. A
variety of output options are then available for use with the
final list of selected structures.
TheCGIapproach[andinthefutureaCORBA(Common
Object Request Broker Architecture)-based approach] will
permit other databases to be integrated into this system, for
example extended data on different protein families. The same
approach could also be applied to include NMR data found in
the BMRB or data found in other community databases.
Database query
Three distinct query interfaces are available for the query of data
within PDB: Status Query (http://www.rcsb.org/pdb/status.html ),
SearchLite (http://www.rcsb.org/pdb/searchlite.html ) and Search-
Fields (http://www.rscb.org/pdb/queryForm.cgi ). Table 3
summarizes the current query and analysis capabilities of the
PDB. Figure 4 illustrates how the various query options are
organized.
SearchLite, which provides a single form field for keyword
searches, was introduced in February 1999. All textual information
within the PDB files as well as dates and some experimental
data are accessible via simple or structured queries. Search-
Fields, accessible since May 1999, is a customizable query
form that allows searching over many different data items
including compound, citation authors, sequence (via a FASTA
search; 16) and release or deposition dates.
Two user interfaces provide extensive information for result
sets from SearchLite or SearchFields queries. The ‘Query
Result Browser’ interface allows for access to some general
information, more detailed information in tabular format, and
the possibility to download whole sets of data files for result
sets consisting of multiple PDB entries. The ‘Structure
Explorer’ interface provides information about individual
structures as well as cross-links to many external resources for
macromolecular structure data (Table 4). Both interfaces are
accessible to other data resources through the simple CGI
application programmer interface (API) described at http://www.
rcsb.org/pdb/linking.html
Figure 4. The various query options that are available for the PDB.
Table 3. Current query capabilities of the PDB
240 Nucleic Acids Research, 2000, Vol. 28, No. 1
The website usage has climbed dramatically since the system
was first introduced in February 1999 (Table 5). As of
November 1, 1999, the main PDB site receives, on average,
greater than one hit per second and greater than one query per
minute.
DATA DISTRIBUTION
The PDB distributes coordinate data, structure factor files and
NMR constraint files. In addition it provides documentation
and derived data. The coordinate data are distributed in PDB
and mmCIF formats. Currently, the PDB file is created as the
final product of data annotation; the program pdb2cif (17) is
used to generate the mmCIF data. This program is used to accom-
modate the legacy data. In the future, both the mmCIF and PDB
format files created during data annotation will be distributed.
Data are distributed to the community in the following ways:
• From primary PDB Web and ftp sites at UCSD, Rutgers and
NIST that are updated weekly.
• From complete Web-based mirror sites that contain all data-
bases, data files, documentation and query interfaces updated
weekly.
• From ftp-only mirror sites that contain a complete or subset
copy of data files, updated at intervals defined by the mirror
site. The steps necessary to create an ftp-only mirror site are
described in http://www.rcsb.org/pdb/ftpproc.final.html
• Quarterly CD-ROM.
Data are distributed once per week. New data officially
become available at 1 a.m. PST each Wednesday. This follows
the tradition developed by BNL and has minimized the impact
of the transition on existing mirror sites. Since May 1999, two
ftp archives have been provided: ftp://ftp.rcsb.org , a reorganized
and more logical organization of all PDB data, software, and
documentation; and ftp://bnlarchive.rcsb.org , a near-identical
copy of the original BNL archive which is maintained for
purposes of backward compatibility. RCSB-style PDB mirrors
have been established in Japan (Osaka University), Singapore
(National University Hospital) and in UK (the Cambridge
Crystallographic Data Centre). Plans call for operating mirrors in
Brazil, Australia, Canada, Germany, and possibly India.
The first PDB CD-ROM distribution by the RCSB contained
the coordinate files,experimental data,software anddocumentation
as found in the PDB on June 30, 1999. Data are currently
distributed as compressed files using the compression utility
program gzip. Refer to http://www.rcsb.org/pdb/cdrom.html
for details of how to order CD-ROM sets. There is presently no
charge for this service.
DATA ARCHIVING
The PDB is establishing a central Master Archiving facility.
The Master Archive plan is based on five goals: reconstruction
of the current archive in case of a major disaster; duplication of
the contents of the PDB as itexistedon aspecific date; preservation
of software, derived data, ancillary data and all other computerized
and printed information; automatic archiving of all depositions
and the PDB production resource; and maintenance of the PDB
correspondence archive that documents all aspects of deposition.
During the transition period, all physical materials including
electronic media and hard copy materials were inventoried and
stored, and are being catalogued.
MAINTENANCE OF THE LEGACY BNL SYSTEM
One of the goals of the PDB has been to provide a smooth
transition from the system at BNL to the new system. Accordingly,
AutoDep, which was developed by BNL (18) for data deposition,
has been ported to the RCSB site and enables depositors to
complete in-progress depositions as well as to make new
depositions. In addition, the EBI accepts data using AutoDep.
Similarly, the programs developed at BNL for data query and
distribution (PDBLite, 3DBbrowser, etc.) are being maintained
by the remaining BNL-style mirrors. The RCSB provides data
in a form usable by these mirrors. Finally the style and format
of the BNL ftp archive is being maintained at ftp://bnlarchive.
rcsb.org
A multitude of resources and programs depend upon their
links to the PDB. To eliminate the risk of interruption to these
services, links to the PDB at BNL were automatically redirected to
the RCSB after BNL closed operations on June 30, 1999 using
Table 4. Static cross-links to other data resources currently provided
by the PDB
Table 5. Web query statistics for the primary RCSB site
(http://www.rcsb.org )
Nucleic Acids Research, 2000, Vol. 28, No. 1 241
a network redirect implemented jointly by RCSB and BNL
staff. While this redirect will be maintained, external resources
linking to the PDB are advised to change any URLs from http://
www.pdb.bnl.gov/ to http://www.rcsb.org/
CURRENT DEVELOPMENTS
In the coming months, the PDB plans to continue to improve
and develop all aspects of data processing. Deposition will be
made easier, and annotation will be more automated. In addition,
software for data deposition and validation will be made available
for in-laboratory use.
The PDB will also continue to develop ways of exchanging
information between databases. The PDB is leading the Object
Management Group Life Sciences Initiative’s efforts to define
a CORBA interface definition for the representation of macro-
molecular structure data. This is a standard developed under a
strict procedure to ensure maximum input by members of
various academic and industrial research communities. At this
stage, proposals for the interface definition, including a
working prototype that uses the standard, are being accepted.
For further details refer to http://www.omg.org/cgi-bin/doc?lifesci/
99-08-15 . The finalized standard interface will facilitate the query
and exchange of structural information not just at the level of
complete structures, but at finer levels of detail. The standard
being proposed by the PDB will conform closely to the mmCIF
standard. It is recognized that other forms of data representation
are desirable, for example using eXtensible Markup Language
(XML). The PDB will continue to work with mmCIF as the
underlying standard from which CORBA and XML represen-
tations can be generated as dictated by the needs of the
community.
The PDB will also develop the means and methods of
communications with the broad PDB user community via the
Web. To date we have developed prototype protein documentaries
(19) that explore this new medium in describing structure–
function relationships in proteins. It is also possible to develop
educational materials that will run using a recent Web browser
(20).
Finally it is recognized that structures exist both in the public
and private domains. To this end we are planning on providing
a subset of database tools for local use. Users will be able to
load both public and proprietary data and use the same search
and exploratory tools used at PDB resources.
The PDB does not exist in isolation, rather each structure
represents a point in a spectrum of information that runs from
the recognition of an open reading frame to a fully understood
role of the single or multiple biological functions of that molecule.
The available information that exists on this spectrum changes
over time. Recognizing this, the PDB has developed a scheme
for the dynamic update of a variety of links on each structure to
whatever else can be automatically located on the Internet.
This information is itself stored in a database and can be
queried. This feature will appear in the coming months to
supplement the existing list of static links to a small number of
the more well known related Internet resources.
PDB ADVISORY BOARDS
The PDB has severaladvisory boards.Each member institution
of the RCSB has its own local PDB Advisory Committee. Each
institution is responsible for implementing the recommendations
of those committees, as well as the recommendations of an
International Advisory Board. Initially, the RCSB presented a
report to the Advisory Board previously convened by BNL. At
their recommendation, a new Board has been approached
which contains previous members and new members. The goal
was to have the Board accurately reflect the depositor and user
communities and thus include experts from many disciplines.
Serious issues of policy are referred to the major scientific
societies, notably the IUCr. The goal is to make decisions
based on input from a broad international community of
experts. The IUCr maintains the mmCIF dictionary as the data
standard upon which the PDB is built.
FOR FURTHER INFORMATION
The PDB seeks to keep the community informed of new develop-
ments via weekly news updates to the Web site, quarterly
newsletters, and a soon to be initiated annual report. Users can
request information at any time by sending mail to info@rcsb.
org . Finally, the pdb-l@rcsb.org listserver provides a community
forum for the discussion of PDB-related issues. Changes to PDB
operations that may affect the community, for example, data
format changes, are posted here and users have 60 days to
discuss the issue before changes are made according to major
consensus. Table 6 indicates how to access these resources.
CONCLUSION
These are exciting and challenging times to be responsible for
the collection, curation and distribution of macromolecular
Table 6. PDB information sources
242 Nucleic Acids Research, 2000, Vol. 28, No. 1
structure data. Since the RCSB assumed responsibility for data
deposition in February 1999, the number of depositions has
averaged approximately 50 per week. However, with the
advent of a number of structure genomics initiatives world-
wide this number is likely to increase. We estimate that the
PDB, which at this writing contains approximately 10 500
structures, could triple or quadruple in size over the next
5 years. This presents a challenge to timely distribution while
maintaining high quality. The PDB’s approach of using
modern data management practices should permit us to scale to
accommodate a large data influx.
The maintenance and further development of the PDB are
community efforts. The willingness of others to share ideas,
software and data provides a depth to the resource not obtainable
otherwise. Some of these efforts are acknowledged below.
New input is constantly being sought and the PDB invites you
to make comments at any time by sending electronic mail to
info@rcsb.org
ACKNOWLEDGEMENTS
Research Collaboratory for Structural Bioinformatics (RCSB) is a
consortium consisting of three institutions: Rutgers University,
San Diego Supercomputer Center at University of California,
San Diego, and the National Institute of Standards and Technology.
The current RCSB PDB staff include the authors indicated and
Kyle Burkhardt, Anke Gelbin, Michael Huang, Shri Jain,
Rachel Kramer, Nate Macapagal, Victoria Colflesh, Bohdan
Schneider, Kata Schneider, Christine Zardecki (Rutgers);
Phoebe Fagan, Diane Hancock, Narmada Thanki, Michael
Tung, Greg Vasquez (NIST); Peter Arzberger, John Badger,
Douglas S. Greer, Michael Gribskov, John Kowalski, Glen
Otero, Shawn Strande, Lynn F. Ten Eyck, Kenneth Yoshimoto
(UCSD). The continuing support of Ken Breslauer (Rutgers),
John Rumble (NIST) and Sid Karin (SDSC) is gratefully
acknowledged. Current collaborators contributing to the future
development of the PDB are the BioMagResBank, the
Cambridge Crystallographic Data Centre, the HIV Protease
Database Group, The Institute for Protein Research, Osaka
University, National Center for Biotechnology Information,
the ReLiBase developers, and the Swiss Institute for Bio-
informatics/Glaxo. We are especially grateful to Kim Henrick
of the EBI and Steve Bryant at NCBI who have reviewed our
files and sent back constructive criticisms. This has helped the
PDB to continuously improve its procedures for producing
entries. The cooperation of the BNL PDB staff is gratefully
acknowledged. Portions of this article will appear in Volume F
of the International Tables of Crystallography. This work is
supported by grants from the National Science Foundation, the
Office of Biology and Environmental Research at the Department
of Energy, and two units of the National Institutes of Health:
the National Institute of General Medical Sciences and the
National Institute of Medicine.
REFERENCES
1. Bernstein,F.C., Koetzle,T.F., Williams,G.J., Meyer,E.E., Brice,M.D.,
Rodgers,J.R., Kennard,O., Shimanouchi,T. and Tasumi,M. (1977)
J. Mol. Biol., 112, 535–542.
2. Bourne,P., Berman,H.M., Watenpaugh,K., Westbrook,J.D. and
Fitzgerald,P.M.D. (1997) Methods Enzymol., 277, 571–590.
3. Westbrook,J. and Bourne,P.E. (2000) Bioinformatics, in press.
4. Markley,J.L., Bax,A., Arata,Y., Hilbers,C.W., Kaptein,R., Sykes,B.D.,
Wright,P.E. and Wüthrich,K. (1998) J. Biomol. NMR, 12, 1–23.
5. Engh,R.A. and Huber,R. (1991) Acta Crystallogr., A47, 392–400.
6. Clowney,L., Jain,S.C., Srinivasan,A.R., Westbrook,J., Olson,W.K. and
Berman,H.M. (1996) J. Am. Chem. Soc., 118, 509–518.
7. Gelbin,A., Schneider,B., Clowney,L., Hsieh,S.-H., Olson,W.K. and
Berman,H.M. (1996) J. Am. Chem. Soc., 118, 519–528.
8. IUPAC–IUB Joint Commission on Biochemical Nomenclature (1983)
Eur. J. Biochem., 131, 9–15.
9. Zhang.J., Cousens,L.S., Barr,P.J. and Sprang,S.R. (1991) Proc. Natl
Acad. Sci. USA, 88, 3346–3450.
10. Laskowski,R.A., McArthur,M.W., Moss,D.S. and Thornton,J.M. (1993)
J. Appl. Crystallogr., 26, 283–291.
11. Vaguine,A.A., Richelle,J.and Wodak,S.J. (1999) Acta Crystallogr.,D55,
191–205.
12. Ulrich,E.L., Markley,J.L andKyogoku,Y. (1989) Protein Seq. Data Anal.,
2, 23–37.
13. Lee,B. and Richards,F.M. (1971) J. Mol. Biol., 55, 379–400.
14. Shindyalov,I.N. and Bourne,P.E. (1998) Protein Eng., 11, 739–747.
15. Gilliland,G.L. (1988) J. Cryst. Growth, 90, 51–59.
16. Pearson,W.R. and Lipman,D.J. (1988) Proc. Natl Acad. Sci. USA, 24,
2444–2448.
17. Bernstein,H.J., Bernstein,F.C. and Bourne,P.E. (1998) J. Appl.
Crystallogr., 31, 282–295.
18. Laboratory,B.N. (1998) AutoDep, version 2.1. Upton, NY.
19. Quinn,G., Taylor,A., Wang,H.-P. and Bourne,P.E. (1999) Trends
Biochem. Sci., 24, 321–324.
20. Quinn,G., Wang,H.-P., Martinez,D. and Bourne,P.E. (1999)
Pacific Symp. Biocomput., 380–391.
21. Siddiqui,A. and Barton,G. (1996) Perspectives on Protein Engineering
1996, 2, (CD-ROM edition; Geisow,M.J. ed.) BIODIGM Ltd (UK).
ISBN 0-9529015-0-1.
22. Orengo,C.A., Michie,A.D., Jones,S., Jones,D.T., Swindels,M.B. and
Thornton,J.M. (1997) Structure, 5, 1093–1108.
23. Kabsch,W. and Sander,C. (1983) Biopolymers, 22, 2277–2637.
24. Holm,L. and Sander,C. (1998) Nucleic Acids Res., 26, 316–319.
25. Nayal,M., Hitz,B.C. and Honig,B. (1999) Protein Sci., 8, 676–679.
26. Dodge,C., Schneider,R. and Sander,C. (1998) Nucleic Acids Res., 26,
313–315.
27. Suhnel,J. (1996) Comput. Appl. Biosci., 12, 227–229.
28. Hogue,C., Ohkawa,H. and Bryant,S. (1996) Trends Biochem. Sci., 21,
226–229.
29. Berman,H.M., Olson,W.K., Beveridge,D.L., Westbrook,J., Gelbin,A.,
Demeny,T., Hsieh,S.H., Srinivasan,A.R. and Schneider,B. (1992)
Biophys. J., 63, 751–759.
30. Weissig,H., Shindyalov,I.N. and Bourne,P.E. (1998) Acta Crystallogr.,
D54, 1085–1094.
31. Laskowski,R.A., Hutchinson,E.G., Michie,A.D., Wallace,A.C.,
Jones,M.L. and Thornton,J.M. (1997) Trends Biochem. Sci., 22, 488–490.
32. Murzin,A.G., Brenner,S.E., Hubbard,T. and Chothia,C. (1995)
J. Mol. Biol., 247, 536–540.
33. Neshich,G., Togawa,R., Vilella,W. and Honig,B. (1998) Protein Data
Bank Quarterly Newsletter, 84.
34. Westhead,D., Slidel,T., Flores,T. and Thornton,J. (1998) Protein Sci., 8,
897–904.
35. Gibrat,J.-F., Madej,T. and Bryant,S.H. (1996) Curr. Opin. Struct. Biol., 6,
377–385.
36. Hooft,R.W.W., Sander,C. and Vriend,G. (1996) J. Appl. Crystallogr., 29,
714–716.
