Michal Hammel

Michal Hammel
Lawrence Berkeley National Laboratory | LBL

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155
Publications
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Publications

Publications (155)
Article
Oligomerization is a core structural feature that defines the form and function of many proteins. Most proteins form molecular complexes; however, there remains a dearth of diversity-driven structural studies investigating the evolutionary trajectory of these assemblies. Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) is one such enzyme t...
Preprint
Rhamnogalacturonan I (RGI) is a structurally complex pectic polysaccharide with a backbone of alternating rhamnose and galacturonic acid residues substituted with arabinan and galactan side chains. Galactan synthase 1 (GalS1), transfers galactose and arabinose to either extend or cap the β-1,4 galactan side chains of RGI, respectively. Here we repo...
Article
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Regulation of bacteriophage gene expression involves repressor proteins that bind and downregulate early lytic promoters. A large group of mycobacteriophages code for repressors that are unusual in also terminating transcription elongation at numerous binding sites (stoperators) distributed across the phage genome. Here we provide the X-ray crystal...
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The RAS–RAF pathway is one of the most commonly dysregulated in human cancers1–3. Despite decades of study, understanding of the molecular mechanisms underlying dimerization and activation⁴ of the kinase RAF remains limited. Recent structures of inactive RAF monomer⁵ and active RAF dimer5–8 bound to 14-3-39,10 have revealed the mechanisms by which...
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Lipid nanoparticles (LNPs) are gaining traction in the field of nucleic acid delivery following the success of two mRNA vaccines against COVID-19. As one of the constituent lipids on LNP surfaces, PEGylated lipids (PEG-lipids) play an important role in defining LNP physicochemical properties and biological interactions. Previous studies indicate th...
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Background COBRA™ (COnditional Bispecific Redirected Activation) T-cell engagers are designed to target solid tumors as a single polypeptide chain prodrug that becomes activated by proteolysis in the tumor microenvironment. One COBRA molecule comprises seven Ig domains: three single-domain antibodies (sdAbs) recognizing a tumor target or human seru...
Article
Complement evasion is a hallmark of extracellular microbial pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. Lyme disease spirochetes express nearly a dozen outer surface lipoproteins that bind complement components and interfere with their native activities. Among these, BBK32 is unique in its selective inhibition of th...
Preprint
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Tyrosyl DNA phosphodiesterase 1 (TDP1) and DNA Ligase IIIα (LigIIIα) are key enzymes in single-strand break (SSB) repair. TDP1 removes 3’-tyrosine residues remaining after degradation of DNA topoisomerase (TOP) 1 cleavage complexes trapped either by DNA lesions or TOP1 inhibitors. It is not known how TDP1 is linked to subsequent processing and LigI...
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Human serum albumin (HSA) constitutes the primary transporter of fatty acids, bilirubin, and other plasma compounds. The binding, transport, and release of its cargos strongly depend on albumin conformation, which is affected by bound ligands induced by physiological and pathological conditions. HSA is both highly oxidized and heavily loaded with f...
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The RNA transcription complex (RTC) from the virus, SARS-CoV-2, is responsible for recognizing and processing RNA for two principal purposes. The RTC copies viral RNA for propagation into new virus and for ribosomal transcription of viral proteins. To accomplish these activities the RTC mechanism must also conform to a large number of imperatives i...
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Evolutionary selection ensures specificity and efficiency in dynamic metastable macromolecular machines that repair DNA damage without releasing toxic and mutagenic intermediates. Here we examine non-homologous end joining (NHEJ) as the primary conserved DNA double-strand break (DSB) repair process in human cells. NHEJ has exemplary key roles in ne...
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Monoclonal antibodies (mAbs) are the basis of treatments and diagnostics for pathogens and other biological phenomena. We conducted a structural characterization of mAbs against the N-terminal domain of nucleocapsid protein (NPNTD) from SARS-CoV-2 using small-angle X-ray scattering and transmission electron microscopy. Our solution-based results di...
Preprint
The complement system is a proteolytic cascade involving dozens of soluble and membrane-associated proteins that function in recognition, opsonization, and elimination of foreign or damaged cells of host origin. Complement evasion is a hallmark of certain human microbial pathogens such as Borreliella burgdorferi , the causative agent of Lyme diseas...
Preprint
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Monoclonal antibodies (mAbs) are the basis of treatments and diagnostics for pathogens and other biological phenomena. We conducted a structural characterization of mAbs against the N-terminal domain of nucleocapsid protein (NP NTD ) from SARS-CoV-2 using small angle X-ray scattering (SAXS). Our solution-based results distinguished the mAbs' flexib...
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ABSTRACT Mechanistic studies in DNA repair have focused on roles of multi-protein DNA complexes, so how long non-coding RNAs (lncRNAs) regulate DNA repair is less well understood. Yet, lncRNA LINP1 is over-expressed in multiple cancers and confers resistance to ionizing radiation and chemotherapeutic drugs. Here, we unveil structural and mechanisti...
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The XRCC1-DNA ligase III␣ complex (XL) is critical for DNA single-strand break repair, a key target for PARP inhibitors in cancer cells deficient in homolo-gous recombination. Here, we combined biophysical approaches to gain insights into the shape and con-formational flexibility of the XL as well as XRCC1 and DNA ligase III␣ (LigIII␣) alone. Struc...
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Assembly of KU and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) at DNA double strand breaks (DSBs) forms DNA-PK holoenzyme as a critical initiating step for non-homologous end joining (NHEJ) repair of DSBs produced by radiation and chemotherapies. Advanced cryo-electron microscopy (cryo-EM) imaging together with breakthrough macromolec...
Article
Heparin and heparan sulfate (HS) are highly sulfated polysaccharides covalently bound to cell surface proteins, which directly interact with many extracellular proteins, including the transforming growth factor-β (TGFβ) family ligand antagonist, follistatin 288 (FS288). Follistatin neutralizes the TGFβ ligands, myostatin and activin A, by forming a...
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DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a key member of the phosphatidylinositol-3 kinase-like (PIKK) family of protein kinases with critical roles in DNA-double strand break repair, transcription, metastasis, mitosis, RNA processing, and innate and adaptive immunity. The absence of DNA-PKcs from many model organisms has led to...
Article
When nanoparticles enter biological environments, proteins adsorb to form the "protein corona" which causes significant changes in biodistribution and toxicity. Herein, we measure protein corona formation on DNA-functionalized single-walled carbon nanotubes (ssDNA-SWCNTs), a nanoparticle ideal for sensing and delivery, in blood plasma and cerebrosp...
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Mechanistic studies in DNA repair have focused on roles of multi-protein DNA complexes, so how long non-coding RNAs (lncRNAs) regulate DNA repair is less well understood. Yet, lncRNA LINP1 is over-expressed in multiple cancers and confers resistance to ionizing radiation and chemotherapeutic drugs. Here, we unveil structural and mechanistic insight...
Article
Full-text available
Rubisco sustains the biosphere through the fixation of CO2 into biomass. In plants and cyanobacteria, form I Rubisco is structurally comprised of large and small subunits, whereas all other Rubisco forms lack small subunits. The rise of the form I complex through the innovation of small subunits represents a key, yet poorly understood, transition i...
Article
Introducing engineered nanoparticles into biosystems leads to formation of the interfacial protein corona, modifying nanoparticle identity and function. Herein, protein corona composition, interactions, and dynamics are analyzed on carbon nanotube‐based sensors. This generic framework will enhance our fundamental understanding of protein corona for...
Article
Nucleoid Remodeling During Environmental Adaptation as Seen Through Soft X-ray Tomography - Michal Hammel
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Xeroderma pigmentosum group G (XPG) protein is both a functional partner in multiple DNA damage responses (DDR) and a pathway coordinator and structure-specific endonuclease in nucleotide excision repair (NER). Different mutations in the XPG gene ERCC5 lead to either of two distinct human diseases: Cancer-prone xeroderma pigmentosum (XP-G) or the f...
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Bacterial nucleoid remodeling dependent on conserved histone-like protein, HU is one of the determining factors in global gene regulation. By imaging of near-native, unlabeled E. coli cells by soft X-ray tomography, we show that HU remodels nucleoids by promoting the formation of a dense condensed core surrounded by less condensed isolated domains....
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The diversity of living cells, in both size and internal complexity, calls for imaging methods with adaptable spatial resolution. Soft x-ray tomography (SXT) is a three-dimensional imaging technique ideally suited to visualizing and quantifying the internal organization of single cells of varying sizes in a near-native state. The achievable resolut...
Preprint
When a nanoparticle enters a biological environment, the surface is rapidly coated with proteins to form a "protein corona". Presence of the protein corona surrounding the nanoparticle has significant implications for applying nanotechnologies within biological systems, affecting outcomes such as biodistribution and toxicity. Herein, we measure pro...
Article
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The XPA protein functions together with the single-stranded DNA (ssDNA) binding protein RPA as the central scaffold to ensure proper positioning of repair factors in multi-protein nucleotide excision repair (NER) machinery. We previously determined the structure of a short motif in the disordered XPA N-terminus bound to the RPA32C domain. However,...
Poster
DNA Ligase III plays a crucial role in nuclear single strand break (SSB) and base excision repair (BER) pathways, as well as in mitochondrial DNA metabolism. In the nucleus, DNA ligase III functions in a complex with the scaffold protein X-ray repair cross-complementing protein 1 (XRCC1), whereas DNA ligase III functions independently of XRCC1 in m...
Article
Recent structural studies on the bacteriophage T7 DNA replication system have shed light on how multiple proteins assemble to copy two antiparallel DNA strands. In T7, acidic C-terminal tails of both the primase-helicase and single-stranded DNA binding protein bind to two basic patches on the DNA polymerase to aid in replisome assembly, processivit...
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Soluble guanylate cyclase (sGC) is the primary receptor for nitric oxide (NO) in mammalian nitric oxide signaling. We determined structures of full-length Manduca sexta sGC in both inactive and active states using cryo-electron microscopy. NO and the sGC-specific stimulator YC-1 induce a 71° rotation of the heme-binding β H-NOX and PAS domains. Rep...
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CRISPR-Cas systems provide bacteria and archaea with programmable immunity against mobile genetic elements. Evolutionary pressure by CRISPR-Cas has driven bacteriophage to evolve small protein inhibitors, anti-CRISPRs (Acrs), that block Cas enzyme function by wide-ranging mechanisms. We show here that the inhibitor AcrVA4 uses a previously undescri...
Preprint
Full-text available
Soluble guanylate cyclase (sGC) is the primary receptor for nitric oxide (NO) in mammalian nitric oxide signaling. We determined structures of full-length Manduca sexta sGC in both inactive and active states using cryo-electron microscopy. NO and the sGC-specific stimulator YC-1 induce a 71° rotation of the heme-binding β H-NOX and PAS domains. Rep...
Article
Full-text available
ASPP (apoptosis-stimulating proteins of p53) proteins bind PP-1c (protein phosphatase 1) and regulate p53 impacting cancer cell growth and apoptosis. Here we determine the crystal structure of the oncogenic ASPP protein, iASPP, bound to PP-1c. The structure reveals a 1:1 complex that relies on interactions of the iASPP SILK and RVxF motifs with PP-...
Article
The interleukin 1 (IL-1) receptor family, whose members contain three immunoglobulin-like domains (D1-D3) in the extracellular region, is responsible for transmitting pleiotropic signals of IL-1 cytokines. The inter-domain flexibility of IL-1 receptors and its functional roles have not been fully elucidated. In this study, we used small-angle X-ray...
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The major mechanism of antibody-mediated neutralization of the Middle East respiratory syndrome coronavirus (MERS-CoV) involves competition with the cellular receptor dipeptidyl peptidase 4 (DPP4) for binding to the receptor-binding domain (RBD) of the spike (S) glycoprotein. Here, we report a unique epitope and unusual neutralizing mechanism of th...
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Fragment crystallizable (Fc) region of immunoglobulin G (IgG) antibody binds to specific Fc receptors (FcγRs) to control antibody effector functions. Currently, engineered specific Fc-FcγR interactions are validated with a static conformation derived from the crystal structure. However, computational evidence suggests that the conformational variab...
Article
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We wish to withdraw the paper by Lee et al. (2017) on the crystal structure of a protein believed to have been AID (activation-induced cytidine deaminase). It has subsequently been shown that the crystal studied was of E. coli RNAbinding protein Hfq, a contaminant in the protein preparation. The associated PDB entry, 5w09, has also been made obsole...
Chapter
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Small-angle X-ray scattering (SAXS) is an increasingly common and useful technique for structural characterization of molecules in solution. A SAXS experiment determines the scattering intensity of a molecule as a function of spatial frequency, termed SAXS profile. SAXS profiles can be utilized in a variety of molecular modeling applications, such...
Article
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The protein-folding mechanism remains a major puzzle in life science. Purified soluble activation-induced cytidine deaminase (AID) is one of the most difficult proteins to obtain. Starting from inclusion bodies containing a C-terminally truncated version of AID (residues 1–153; AID ¹⁵³ ), an optimized in vitro folding procedure was derived to obtai...
Article
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Non-homologous end joining (NHEJ) repairs DNA double strand breaks in non-cycling eukaryotic cells. NHEJ relies on polynucleotide kinase/phosphatase (PNKP), which generates 5΄-phosphate/3΄-hydroxyl DNA termini that are critical for ligation by the NHEJ DNA ligase, LigIV. PNKP and LigIV require the NHEJ scaffolding protein, XRCC4. The PNKP FHA domai...
Article
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Background: Fusion of the human IgG1 Fc domain to the C-terminal C2 domain of B domain-deleted (BDD) factor VIII (FVIII) results in the rFVIIIFc fusion protein that has a 1.5-fold longer half-life in humans. Objective: To assess the structural properties of rFVIIIFc by comparing its constituent FVIII and Fc elements with their respective isolate...
Poster
Full-text available
The LIG3 gene encodes multiple DNA ligase polypeptides that includes nuclear, mitochondrial (DNA LigIII⍺) and germ line (DNA LigIIIβ) versions of the protein1,2. Nuclear DNA LigIII⍺ forms a stable complex with the scaffold protein XRCC1 (X-ray repair cross-complementing protein 1) that mediates interactions with other repair proteins3. Structural a...
Article
The physical organization of DNA enzymes at a repli- cation fork enables efficient copying of two antipar- allel DNA strands, yet dynamic protein interactions within the replication complex complicate replisome structural studies. We employed a combination of crystallographic, native mass spectrometry and small-angle X-ray scattering experiments to...
Article
Full-text available
DNA double-strand break (DSB) repair by non-homologous end joining (NHEJ) in human cells is initiated by Ku heterodimer binding to a DSB, followed by recruitment of core NHEJ factors including DNA-dependent protein kinase catalytic subunit (DNA-PKcs), XRCC4-like factor (XLF) and XRCC4 (X4)-DNA ligase IV (L4). In addition, Ku interacts with accessor...