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ABSTRACT: Human saposins are essential proteins required for degradation of sphingolipids and lipid antigen presentation. Despite the conserved structural organization of saposins, their distinct modes of interaction with biological membranes are not fully understood. We describe two crystal structures of human saposin C in an "open" configuration with unusual domain swapped homodimers. This form of SapC dimer supports the "clip-on" model for SapC-induced vesicle fusion. In addition, we present the crystal structure of SapD in two crystal forms. They reveal the monomer-monomer interface for the SapD dimer, which was confirmed in solution by analytical ultracentrifugation. The crystal structure of SapD suggests that side chains of Lys10 and Arg17 are involved in initial association with the preferred anionic biological membranes by forming salt bridges with sulfate or phosphate lipid headgroups.
Structure 06/2008; 16(5):809-17. · 6.35 Impact Factor
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ABSTRACT: ArtJ is the substrate-binding component (receptor) of the ATP-binding cassette (ABC) transport system ArtJ-(MP)(2) from the thermophilic bacterium Geobacillus stearothermophilus that is specific for arginine, lysine, and histidine. The highest affinity is found for arginine (K(d)=0.039(+/-0.014) microM), while the affinities for lysine and histidine are about tenfold lower. We have determined the X-ray structures of ArtJ liganded with each of these substrates at resolutions of 1.79 A (arginine), 1.79 A (lysine), and 2.35 A (histidine), respectively. As found for other solute receptors, the polypeptide chain is folded into two distinct domains (lobes) connected by a hinge. The interface between the lobes forms the substrate-binding pocket whose geometry is well preserved in all three ArtJ/amino acid complexes. Structure-derived mutational analyses indicated the crucial role of a region in the carboxy-terminal lobe of ArtJ in contacting the transport pore Art(MP)(2) and revealed the functional importance of Gln132 and Trp68. While variant Gln132Leu exhibited lower binding affinity for arginine but no binding of lysine and histidine, the variant Trp68Leu had lost binding activity for all three substrates. The results are discussed in comparison with known structures of homologous proteins from mesophilic bacteria.
Journal of Molecular Biology 02/2008; 375(2):448-59. · 4.00 Impact Factor
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ABSTRACT: Catabolite control protein A (CcpA) functions as master transcriptional regulator of carbon catabolism in Firmicutes. It belongs to the family of bacterial repressor/regulator proteins. Here, the crystal structure of the 76 kDa homodimeric CcpA protein from Lactococcus lactis subsp. lactis IL1403 is presented at 1.9 A resolution in the absence of cognate DNA. The phases were derived by molecular replacement and the structure was refined to crystallographic R and R(free) factors of 0.177 and 0.211, respectively. The presence of a sulfate molecule in the direct vicinity of a putative effector-binding site in the monomer allowed the derivation of a model for the possible binding of small organic effector molecules.
Acta Crystallographica Section D Biological Crystallography 05/2007; 63(Pt 4):431-6. · 12.62 Impact Factor
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Martin Hülsmeyer,
Patrick Chames,
Roman C Hillig,
Robyn L Stanfield,
Gerhard Held,
Pierre G Coulie, Claudia Alings,
Gabriele Wille,
Wolfram Saenger,
Barbara Uchanska-Ziegler,
Hennie R Hoogenboom,
Andreas Ziegler
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ABSTRACT: Antibodies with T cell receptor-like specificity possess a considerable diagnostic and therapeutic potential, but the structural basis of the interaction between an antibody and an histocompatibility antigen has so far not been determined. We present here the crystal structure (at 2.15 A resolution) of the recombinant, affinity-matured human antibody fragment Fab-Hyb3 bound to the tumor-associated human leukocyte antigen (HLA)/peptide complex HLA-A1.MAGE-A1. Fab-Hyb3 employs a diagonal docking mode resembling that of T cell receptors. However, other than these natural ligands, the antibody uses only four of its six complementarity-determining regions for direct interactions with the target. It recognizes the C-terminal half of the MAGE-A1 peptide, the HLA-A1 alpha1-helix, and N-terminal residues of the alpha2-helix, accompanied by a large tilting angle between the two types of molecules within the complex. Interestingly, only a single hydrogen bond between a peptide side chain and Fab-Hyb3 contributes to the interaction, but large buried surface areas with pronounced shape complementarity assure high affinity and specificity for MAGE-A1. The HLA-A1.MAGE-A1.antibody structure is discussed in comparison with those of natural ligands recognizing HLA.peptide complexes.
Journal of Biological Chemistry 01/2005; 280(4):2972-80. · 4.77 Impact Factor
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Martin Hülsmeyer,
Patrick Chames,
Roman C. Hillig,
Robyn L. Stanfield,
Gerhard Held,
Pierre G. Coulie, Claudia Alings,
Gabriele Wille,
Wolfram Saenger,
Barbara Uchanska-Ziegler,
Hennie R. Hoogenboom,
Andreas Ziegler
[show abstract]
[hide abstract]
ABSTRACT: Antibodies with T cell receptor-like specificity possess a considerable diagnostic and therapeutic potential, but the structural
basis of the interaction between an antibody and an histocompatibility antigen has so far not been determined. We present
here the crystal structure (at 2.15 Å resolution) of the recombinant, affinity-matured human antibody fragment Fab-Hyb3 bound
to the tumor-associated human leukocyte antigen (HLA)/peptide complex HLA-A1·MAGE-A1. Fab-Hyb3 employs a diagonal docking
mode resembling that of T cell receptors. However, other than these natural ligands, the antibody uses only four of its six
complementarity-determining regions for direct interactions with the target. It recognizes the C-terminal half of the MAGE-A1
peptide, the HLA-A1 α1-helix, and N-terminal residues of the α2-helix, accompanied by a large tilting angle between the two
types of molecules within the complex. Interestingly, only a single hydrogen bond between a peptide side chain and Fab-Hyb3
contributes to the interaction, but large buried surface areas with pronounced shape complementarity assure high affinity
and specificity for MAGE-A1. The HLA-A1·MAGE-A1·antibody structure is discussed in comparison with those of natural ligands
recognizing HLA·peptide complexes.
Journal of Biological Chemistry 01/2005; 280(4):2972-2980. · 4.77 Impact Factor
