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Zhang Y, Vontz AJ, Kallenberger EM, Xu X, Ploscariu NT, Ramyar KX, Garcia BL, Ghebrehiwet B, Geisbrecht BV. gC1qR/C1qBP/HABP-1: Structural Analysis of the Trimeric Core Region, Interactions With a Novel Panel of Monoclonal Antibodies, and Their Influence on Binding to FXII. Front Immunol 2022; 13:887742. [PMID: 35865516 PMCID: PMC9294231 DOI: 10.3389/fimmu.2022.887742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 06/06/2022] [Indexed: 01/01/2023] Open
Abstract
The protein gC1qR/C1qBP/HABP-1 plays an essential role in mitochondrial biogenesis, but becomes localized at the cellular surface in numerous pathophysiological states. When this occurs on endothelial cells, surface-exposed gC1qR activates the classical pathway of complement. It also promotes assembly of a multi-protein complex comprised of coagulation factor XII (FXII), pre-kallikrein (PK), and high-molecular weight kininogen (HMWK) that activates the contact system and the kinin-generating system. Since surface-exposed gC1qR triggers intravascular inflammatory pathways, there is interest in identifying molecules that block gC1qR function. Here we further that objective by reporting the outcome of a structure/function investigation of gC1qR, its interactions with FXII, and the impact of a panel of monoclonal anti-gC1qR antibodies on FXII binding to gC1qR. Although deletion mutants have been used extensively to assess gC1qR function, none of these proteins have been characterized structurally. To that end, we determined a 2.2 Å resolution crystal structure of a gC1qR mutant lacking both of its acidic loops, but which retained nanomolar-affinity binding to FXII and FXIIa. This structure revealed that the trimeric gC1qR assembly was maintained despite loss of roughly thirty residues. Characterization of a novel panel of anti-gC1qR monoclonal antibodies identified several with biochemical properties distinct from previously described antibodies, as well as one which bound to the first acidic loop of gC1qR. Intriguingly, we found that each of these antibodies could partly inhibit binding of FXII and FXIIa to gC1qR. Based on these results and previously published studies, we offer new perspectives for developing gC1qR inhibitors.
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Affiliation(s)
- Ying Zhang
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Alexander J. Vontz
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Ethan M. Kallenberger
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Xin Xu
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Nicoleta T. Ploscariu
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Kasra X. Ramyar
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Brandon L. Garcia
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States
| | - Berhane Ghebrehiwet
- Department of Medicine, Stony Brook University, Stony Brook, NY, United States,*Correspondence: Berhane Ghebrehiwet, ; Brian V. Geisbrecht,
| | - Brian V. Geisbrecht
- Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS, United States,*Correspondence: Berhane Ghebrehiwet, ; Brian V. Geisbrecht,
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2
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Ramyar KX, Xu X, White NM, Keightley A, Geisbrecht BV. Expression, purification, and characterization of a human complement component C3 analog that lacks the C-terminal C345c domain. J Immunol Methods 2019; 473:112633. [PMID: 31319063 DOI: 10.1016/j.jim.2019.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/27/2019] [Accepted: 07/11/2019] [Indexed: 10/26/2022]
Abstract
The complement system consists of a series of soluble and cell-surface proteins that serve numerous roles in innate immunity, development, and homeostasis. Despite its many functions, the central event in the complement system is the proteolytic activation of the 185 kDa complement component 3 (C3) into its opsonin and anaphylatoxin fragments known as C3b (175 kDa) and C3a (10 kDa), respectively. The C3 protein is comprised of thirteen separate structural domains, several of which undergo extensive structural rearrangement upon activation to C3b. In addition to this, the C-terminal C345c domain found in C3, C3b, and the terminal degradation product, C3c (135 kDa), appears to adopt multiple conformations relative to the remainder of the molecule. To facilitate various structure/function studies, we designed two C3 analogs that could be activated to a C345c-less, C3c-like state following treatment with Tobacco Etch Virus (TEV) protease. We generated stably transfected Chinese Hamster Ovary (CHO) cell lines that secrete approximately 1.5 mg of the highest-expressing C3 analog per liter of conditioned culture medium. We purified this C3 analog by sequential immobilized metal ion affinity and size exclusion chromatographies, activated the protein by digestion with TEV protease, and purified the resulting C3c analog by a final size exclusion chromatography. The conformations and activities of our C3 and C3c analogs were assessed by measuring their binding profiles to known C3/b/c ligands by surface plasmon resonance. Together, this work demonstrates the feasibility of producing a C3 analog that can be site-specifically activated by an exogenous proteolytic enzyme.
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Affiliation(s)
- Kasra X Ramyar
- Department of Biochemistry & Molecular Biophysics, Kansas State University, 141 Chalmers Hall, 1711 Claflin Road, Manhattan, KS 66506, United States of America
| | - Xin Xu
- Department of Biochemistry & Molecular Biophysics, Kansas State University, 141 Chalmers Hall, 1711 Claflin Road, Manhattan, KS 66506, United States of America
| | - Natalie M White
- Department of Biochemistry & Molecular Biophysics, Kansas State University, 141 Chalmers Hall, 1711 Claflin Road, Manhattan, KS 66506, United States of America
| | - Andrew Keightley
- School of Biological Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, MO 64110, United States of America
| | - Brian V Geisbrecht
- Department of Biochemistry & Molecular Biophysics, Kansas State University, 141 Chalmers Hall, 1711 Claflin Road, Manhattan, KS 66506, United States of America.
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3
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Barta ML, Tachiyama S, Muthuramalingam M, Arizmendi O, Villanueva CE, Ramyar KX, Geisbrecht BV, Lovell S, Battaile KP, Picking WL, Picking WD. Using disruptive insertional mutagenesis to identify the in situ structure-function landscape of the Shigella translocator protein IpaB. Protein Sci 2018; 27:1392-1406. [PMID: 29672980 DOI: 10.1002/pro.3428] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/12/2018] [Accepted: 04/16/2018] [Indexed: 11/11/2022]
Abstract
Bacterial type III secretion systems (T3SS) are used to inject proteins into mammalian cells to subvert cellular functions. The Shigella T3SS apparatus (T3SA) is comprised of a basal body, cytoplasmic sorting platform and exposed needle with needle "tip complex" (TC). TC maturation occurs when the translocator protein IpaB is recruited to the needle tip where both IpaD and IpaB control secretion induction. IpaB insertion into the host membrane is the first step of translocon pore formation and secretion induction. We employed disruptive insertional mutagenesis, using bacteriophage T4 lysozyme (T4L), within predicted IpaB loops to show how topological features affect TC functions (secretion control, translocon formation and effector secretion). Insertions within the N-terminal half of IpaB were most likely to result in a loss of steady-state secretion control, however, all but the two that were not recognized by the T3SA retained nearly wild-type hemolysis (translocon formation) and invasiveness levels (effector secretion). In contrast, all but one insertion in the C-terminal half of IpaB maintained secretion control but were impaired for hemolysis and invasion. These nature of the data suggest the latter mutants are defective in a post-secretion event, most likely due to impaired interactions with the second translocator protein IpaC. Intriguingly, only two insertion mutants displayed readily detectable T4L on the bacterial surface. The data create a picture in which the makeup and structure of a functional T3SA TC is highly amenable to physical perturbation, indicating that the tertiary structure of IpaB within the TC is more plastic than previously realized.
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Affiliation(s)
- Michael L Barta
- Higuchi Biosciences Center, University of Kansas, Lawrence, Kansas, 66047
| | - Shoichi Tachiyama
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045
| | | | - Olivia Arizmendi
- Higuchi Biosciences Center, University of Kansas, Lawrence, Kansas, 66047
| | - Cecilia E Villanueva
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045
| | - Kasra X Ramyar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Brian V Geisbrecht
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Scott Lovell
- Protein Structure Laboratory, Del Shankel Structural Biology Center, University of Kansas, Lawrence, KS, 66045
| | - Kevin P Battaile
- IMCA-CAT, Hauptman-Woodward Medical Research Institute, Argonne, Illinois, 60439
| | - Wendy L Picking
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
| | - William D Picking
- Higuchi Biosciences Center, University of Kansas, Lawrence, Kansas, 66047.,Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, 66047
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4
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de Jong NWM, Ploscariu NT, Ramyar KX, Garcia BL, Herrera AI, Prakash O, Katz BB, Leidal KG, Nauseef WM, van Kessel KPM, van Strijp JAG, Geisbrecht BV. A structurally dynamic N-terminal region drives function of the staphylococcal peroxidase inhibitor (SPIN). J Biol Chem 2018; 293:2260-2271. [PMID: 29306874 PMCID: PMC5818189 DOI: 10.1074/jbc.ra117.000134] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/21/2017] [Indexed: 01/07/2023] Open
Abstract
The heme-containing enzyme myeloperoxidase (MPO) is critical for optimal antimicrobial activity of human neutrophils. We recently discovered that the bacterium Staphylococcus aureus expresses a novel immune evasion protein, called SPIN, that binds tightly to MPO, inhibits MPO activity, and contributes to bacterial survival following phagocytosis. A co-crystal structure of SPIN bound to MPO suggested that SPIN blocks substrate access to the catalytic heme by inserting an N-terminal β-hairpin into the MPO active-site channel. Here, we describe a series of experiments that more completely define the structure/function relationships of SPIN. Whereas the SPIN N terminus adopts a β-hairpin confirmation upon binding to MPO, the solution NMR studies presented here are consistent with this region of SPIN being dynamically structured in the unbound state. Curiously, whereas the N-terminal β-hairpin of SPIN accounts for ∼55% of the buried surface area in the SPIN-MPO complex, its deletion did not significantly change the affinity of SPIN for MPO but did eliminate the ability of SPIN to inhibit MPO. The flexible nature of the SPIN N terminus rendered it susceptible to proteolytic degradation by a series of chymotrypsin-like proteases found within neutrophil granules, thereby abrogating SPIN activity. Degradation of SPIN was prevented by the S. aureus immune evasion protein Eap, which acts as a selective inhibitor of neutrophil serine proteases. Together, these studies provide insight into MPO inhibition by SPIN and suggest possible functional synergy between two distinct classes of S. aureus immune evasion proteins.
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Affiliation(s)
- Nienke W. M. de Jong
- From Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Nicoleta T. Ploscariu
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Kasra X. Ramyar
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Brandon L. Garcia
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Alvaro I. Herrera
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Om Prakash
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Benjamin B. Katz
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Kevin G. Leidal
- the Inflammation Program, Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52240, and
| | - William M. Nauseef
- the Inflammation Program, Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52240, and ,the Iowa City Veterans Affairs Health Care System, Iowa City, Iowa 52246
| | - Kok P. M. van Kessel
- From Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Jos A. G. van Strijp
- From Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Brian V. Geisbrecht
- the Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, , To whom correspondence should be addressed:
Dept. of Biochemistry and Molecular Biophysics, Kansas State University, 141 Chalmers Hall, 1711 Claflin Rd., Manhattan, KS 66506. Tel.:
785-532-3154; Fax:
785-532-7278; E-mail:
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5
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de Jong NWM, Ramyar KX, Guerra FE, Nijland R, Fevre C, Voyich JM, McCarthy AJ, Garcia BL, van Kessel KPM, van Strijp JAG, Geisbrecht BV, Haas PJA. Immune evasion by a staphylococcal inhibitor of myeloperoxidase. Proc Natl Acad Sci U S A 2017; 114:9439-9444. [PMID: 28808028 PMCID: PMC5584439 DOI: 10.1073/pnas.1707032114] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is highly adapted to its host and has evolved many strategies to resist opsonization and phagocytosis. Even after uptake by neutrophils, S. aureus shows resistance to killing, which suggests the presence of phagosomal immune evasion molecules. With the aid of secretome phage display, we identified a highly conserved protein that specifically binds and inhibits human myeloperoxidase (MPO), a major player in the oxidative defense of neutrophils. We have named this protein "staphylococcal peroxidase inhibitor" (SPIN). To gain insight into inhibition of MPO by SPIN, we solved the cocrystal structure of SPIN bound to a recombinant form of human MPO at 2.4-Å resolution. This structure reveals that SPIN acts as a molecular plug that prevents H2O2 substrate access to the MPO active site. In subsequent experiments, we observed that SPIN expression increases inside the neutrophil phagosome, where MPO is located, compared with outside the neutrophil. Moreover, bacteria with a deleted gene encoding SPIN showed decreased survival compared with WT bacteria after phagocytosis by neutrophils. Taken together, our results demonstrate that S. aureus secretes a unique proteinaceous MPO inhibitor to enhance survival by interfering with MPO-mediated killing.
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Affiliation(s)
- Nienke W M de Jong
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Kasra X Ramyar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506
| | - Fermin E Guerra
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717
| | - Reindert Nijland
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
- Laboratory of Phytopathology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Cindy Fevre
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Jovanka M Voyich
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717
| | - Alex J McCarthy
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Brandon L Garcia
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506
| | - Kok P M van Kessel
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | - Jos A G van Strijp
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands;
| | - Brian V Geisbrecht
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506
| | - Pieter-Jan A Haas
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
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6
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Woehl JL, Ramyar KX, Katz BB, Walker JK, Geisbrecht BV. The structural basis for inhibition of the classical and lectin complement pathways by S. aureus extracellular adherence protein. Protein Sci 2017; 26:1595-1608. [PMID: 28512867 DOI: 10.1002/pro.3195] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/10/2017] [Accepted: 05/10/2017] [Indexed: 01/07/2023]
Abstract
The extracellular adherence protein (Eap) plays a crucial role in pathogenesis and survival of Staphylococcus aureus by inhibiting the classical and lectin pathways of complement. We have previously shown that Eap binds with nanomolar affinity to complement C4b and disrupts the initial interaction between C4b and C2, thereby inhibiting formation of the classical and lectin pathway C3 pro-convertase. Although an underlying mechanism has been identified, the structural basis for Eap binding to C4b is poorly understood. Here, we show that Eap domains 3 and 4 each contain a low-affinity, but saturable binding site for C4b. Taking advantage of the high lysine content of Eap, we used a zero-length crosslinking approach to map the Eap binding site to both the α'- and γ-chains of C4b. We also probed the C4b/Eap interface through a chemical footprinting approach involving lysine modification, proteolytic digestion, and mass spectrometry. This identified seven lysines in Eap that undergo changes in solvent exposure upon C4b binding. We found that simultaneous mutation of these lysines to either alanine or glutamate diminished C4b binding and complement inhibition by Eap. Together, our results provide insight into Eap recognition of C4b, and suggest that the repeating domains that comprise Eap are capable of multiple ligand-binding modes.
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Affiliation(s)
- Jordan L Woehl
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Kasra X Ramyar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Benjamin B Katz
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - John K Walker
- Department of Pharmacology and Physiology, St. Louis University School of Medicine, St. Louis, Missouri, 63104
| | - Brian V Geisbrecht
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
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7
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Shrestha R, Chen X, Ramyar KX, Hayati Z, Carlson EA, Bossmann SH, Song L, Geisbrecht BV, Li P. Identification of Surface-Exposed Protein Radicals and A Substrate Oxidation Site in A-Class Dye-Decolorizing Peroxidase from Thermomonospora curvata. ACS Catal 2016; 6:8036-8047. [PMID: 29308294 DOI: 10.1021/acscatal.6b01952] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dye-decolorizing peroxidases (DyPs) are a family of heme peroxidases, in which a catalytic distal aspartate is involved in H2O2 activation to catalyze oxidations in acidic conditions. They have received much attention due to their potential applications in lignin compound degradation and biofuel production from biomass. However, the mode of oxidation in bacterial DyPs remains unknown. We have recently reported that the bacterial TcDyP from Thermomonospora curvata is among the most active DyPs and shows activity toward phenolic lignin model compounds (J. Biol. Chem.2015, 290, 23447). Based on the X-ray crystal structure solved at 1.75 Å, sigmoidal steady-state kinetics with Reactive Blue 19 (RB19), and formation of compound II-like product in the absence of reducing substrates observed with stopped-flow spectroscopy and electron paramagnetic resonance (EPR), we hypothesized that the TcDyP catalyzes oxidation of large-size substrates via multiple surface-exposed protein radicals. Among 7 tryptophans and 3 tyrosines in TcDyP consisting of 376 residues for the matured protein, W263, W376, and Y332 were identified as surface-exposed protein radicals. Only the W263 was also characterized as one of surface-exposed oxidation sites. SDS-PAGE and size-exclusion chromatography demonstrated that W376 represents an off-pathway destination for electron transfer, resulting in the crosslinking of proteins in the absence of substrates. Mutation of W376 improved compound I stability and overall catalytic efficiency toward RB19. While Y332 is highly conserved across all four classes of DyPs, its catalytic function in A-class TcDyP is minimal possibly due to its extremely small solvent accessible areas. Identification of surface-exposed protein radicals and substrate oxidation sites is important for understanding DyP mechanism and modulating its catalytic functions for improved activity on phenolic lignin.
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Affiliation(s)
| | | | | | - Zahra Hayati
- National
High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | | | | | - Likai Song
- National
High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
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8
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Bannantine JP, Lingle CK, Adam PR, Ramyar KX, McWhorter WJ, Stabel JR, Picking WD, Geisbrecht BV. NlpC/P60 domain-containing proteins of Mycobacterium avium subspecies paratuberculosis that differentially bind and hydrolyze peptidoglycan. Protein Sci 2016; 25:840-51. [PMID: 26799947 DOI: 10.1002/pro.2884] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 01/14/2016] [Accepted: 01/19/2016] [Indexed: 01/22/2023]
Abstract
A subset of proteins containing NlpC/P60 domains are bacterial peptidoglycan hydrolases that cleave noncanonical peptide linkages and contribute to cell wall remodeling as well as cell separation during late stages of division. Some of these proteins have been shown to cleave peptidoglycan in Mycobacterium tuberculosis and play a role in Mycobacterium marinum virulence of zebra fish; however, there are still significant knowledge gaps concerning the molecular function of these proteins in Mycobacterium avium subspecies paratuberculosis (MAP). The MAP genome sequence encodes five NlpC/P60 domain-containing proteins. We describe atomic resolution crystal structures of two such MAP proteins, MAP_1272c and MAP_1204. These crystal structures, combined with functional assays to measure peptidoglycan cleavage activity, led to the observation that MAP_1272c does not have a functional catalytic core for peptidoglycan hydrolysis. Furthermore, the structure and sequence of MAP_1272c demonstrate that the catalytic residues normally required for hydrolysis are absent, and the protein does not bind peptidoglycan as efficiently as MAP_1204. While the NlpC/P60 catalytic triad is present in MAP_1204, changing the catalytic cysteine-155 residue to a serine significantly diminished catalytic activity, but did not affect binding to peptidoglycan. Collectively, these findings suggest a broader functional repertoire for NlpC/P60 domain-containing proteins than simply hydrolases.
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Affiliation(s)
- John P Bannantine
- National Animal Disease Center, USDA-Agricultural Research Service, Ames, Iowa
| | - Cari K Lingle
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri
| | - Philip R Adam
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma
| | - Kasra X Ramyar
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri
| | - William J McWhorter
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri
| | - Judith R Stabel
- National Animal Disease Center, USDA-Agricultural Research Service, Ames, Iowa
| | - William D Picking
- Department of Microbiology & Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma
| | - Brian V Geisbrecht
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri
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9
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Woehl JL, Stapels DAC, Garcia BL, Ramyar KX, Keightley A, Ruyken M, Syriga M, Sfyroera G, Weber AB, Zolkiewski M, Ricklin D, Lambris JD, Rooijakkers SHM, Geisbrecht BV. The extracellular adherence protein from Staphylococcus aureus inhibits the classical and lectin pathways of complement by blocking formation of the C3 proconvertase. J Immunol 2014; 193:6161-6171. [PMID: 25381436 DOI: 10.4049/jimmunol.1401600] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The pathogenic bacterium Staphylococcus aureus actively evades many aspects of human innate immunity by expressing a series of small inhibitory proteins. A number of these proteins inhibit the complement system, which labels bacteria for phagocytosis and generates inflammatory chemoattractants. Although the majority of staphylococcal complement inhibitors act on the alternative pathway to block the amplification loop, only a few proteins act on the initial recognition cascades that constitute the classical pathway (CP) and lectin pathway (LP). We screened a collection of recombinant, secreted staphylococcal proteins to determine whether S. aureus produces other molecules that inhibit the CP and/or LP. Using this approach, we identified the extracellular adherence protein (Eap) as a potent, specific inhibitor of both the CP and LP. We found that Eap blocked CP/LP-dependent activation of C3, but not C4, and that Eap likewise inhibited deposition of C3b on the surface of S. aureus cells. In turn, this significantly diminished the extent of S. aureus opsonophagocytosis and killing by neutrophils. This combination of functional properties suggested that Eap acts specifically at the level of the CP/LP C3 convertase (C4b2a). Indeed, we demonstrated a direct, nanomolar-affinity interaction of Eap with C4b. Eap binding to C4b inhibited binding of both full-length C2 and its C2b fragment, which indicated that Eap disrupts formation of the CP/LP C3 proconvertase (C4b2). As a whole, our results demonstrate that S. aureus inhibits two initiation routes of complement by expression of the Eap protein, and thereby define a novel mechanism of immune evasion.
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Affiliation(s)
- Jordan L Woehl
- Department of Biochemistry & Molecular Biophysics; Kansas State University, Manhattan, KS, USA
| | - Daphne A C Stapels
- Medical Microbiology; University Medical Center Utrecht, Utrecht, The Netherlands
| | - Brandon L Garcia
- School of Biological Sciences; University of Missouri-Kansas City, Kansas City, MO, USA
| | - Kasra X Ramyar
- Department of Biochemistry & Molecular Biophysics; Kansas State University, Manhattan, KS, USA
| | - Andrew Keightley
- School of Biological Sciences; University of Missouri-Kansas City, Kansas City, MO, USA
| | - Maartje Ruyken
- Medical Microbiology; University Medical Center Utrecht, Utrecht, The Netherlands
| | - Maria Syriga
- Department of Pathology & Laboratory Medicine; University of Pennsylvania, Philadelphia, PA, USA
| | - Georgia Sfyroera
- Department of Pathology & Laboratory Medicine; University of Pennsylvania, Philadelphia, PA, USA
| | - Alexander B Weber
- School of Biological Sciences; University of Missouri-Kansas City, Kansas City, MO, USA
| | - Michal Zolkiewski
- Department of Biochemistry & Molecular Biophysics; Kansas State University, Manhattan, KS, USA
| | - Daniel Ricklin
- Department of Pathology & Laboratory Medicine; University of Pennsylvania, Philadelphia, PA, USA
| | - John D Lambris
- Department of Pathology & Laboratory Medicine; University of Pennsylvania, Philadelphia, PA, USA
| | | | - Brian V Geisbrecht
- School of Biological Sciences; University of Missouri-Kansas City, Kansas City, MO, USA.,Department of Biochemistry & Molecular Biophysics; Kansas State University, Manhattan, KS, USA
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10
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Garcia BL, Summers BJ, Ramyar KX, Tzekou A, Lin Z, Ricklin D, Lambris JD, Laity JH, Geisbrecht BV. A structurally dynamic N-terminal helix is a key functional determinant in staphylococcal complement inhibitor (SCIN) proteins. J Biol Chem 2013; 288:2870-81. [PMID: 23233676 PMCID: PMC3554951 DOI: 10.1074/jbc.m112.426858] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Complement is a network of interacting circulatory and cell surface proteins that recognizes, marks, and facilitates clearance of microbial invaders. To evade complement attack, the pathogenic organism Staphylococcus aureus expresses a number of secreted proteins that interfere with activation and regulation of the complement cascade. Staphylococcal complement inhibitors (SCINs) are one important class of these immunomodulators and consist of three active members (SCIN-A/-B/-C). SCINs inhibit a critical enzymatic complex, the alternative pathway C3 convertase, by targeting a functional "hot spot" on the central opsonin of complement, C3b. Although N-terminal truncation mutants of SCINs retain complement inhibitory properties, they are significantly weaker binders of C3b. To provide a structural basis for this observation, we undertook a series of crystallographic and NMR dynamics studies on full-length SCINs. This work reveals that N-terminal SCIN domains are characterized by a conformationally dynamic helical motif. C3b binding and functional experiments further demonstrate that this sequence-divergent N-terminal region of SCINs is both functionally important and context-dependent. Finally, surface plasmon resonance data provide evidence for the formation of inhibitor·enzyme·substrate complexes ((SCIN·C3bBb)·C3). Similar to the (SCIN·C3bBb)(2) pseudodimeric complexes, ((SCIN·C3bBb)·C3) interferes with the interaction of complement receptors and C3b. This activity provides an additional mechanism by which SCIN couples convertase inhibition to direct blocking of phagocytosis. Together, these data suggest that tethering multi-host protein complexes by small modular bacterial inhibitors may be a global strategy of immune evasion used by S. aureus. The work presented here provides detailed structure-activity relationships and improves our understanding of how S. aureus circumvents human innate immunity.
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Affiliation(s)
- Brandon L Garcia
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri, Kansas City, Missouri 64110, USA
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Stapels DA, Ramyar KX, Ricklin D, Milder FJ, Bischoff M, Herrmann M, Geisbrecht BV, Lambris JD, von Köckritz-Blickwede M, Kessel KPV, Rooijakkers SH. Extracellular adherence protein (Eap) of Staphylococcus aureus evades innate immunity by inhibiting complement activation and neutrophil elastase. Immunobiology 2012. [DOI: 10.1016/j.imbio.2012.08.118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Skaff DA, Ramyar KX, McWhorter WJ, Barta ML, Geisbrecht BV, Miziorko HM. Biochemical and structural basis for inhibition of Enterococcus faecalis hydroxymethylglutaryl-CoA synthase, mvaS, by hymeglusin. Biochemistry 2012; 51:4713-22. [PMID: 22510038 DOI: 10.1021/bi300037k] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hymeglusin (1233A, F244, L-659-699) is established as a specific β-lactone inhibitor of eukaryotic hydroxymethylglutaryl-CoA synthase (HMGCS). Inhibition results from formation of a thioester adduct to the active site cysteine. In contrast, the effects of hymeglusin on bacterial HMG-CoA synthase, mvaS, have been minimally characterized. Hymeglusin blocks growth of Enterococcus faecalis. After removal of the inhibitor from culture media, a growth curve inflection point at 3.1 h is observed (vs 0.7 h for the uninhibited control). Upon hymeglusin inactivation of purified E. faecalis mvaS, the thioester adduct is more stable than that measured for human HMGCS. Hydroxylamine cleaves the thioester adduct; substantial enzyme activity is restored at a rate that is 8-fold faster for human HMGCS than for mvaS. Structural results explain these differences in enzyme-inhibitor thioester adduct stability and solvent accessibility. The E. faecalis mvaS-hymeglusin cocrystal structure (1.95 Å) reveals virtually complete occlusion of the bound inhibitor in a narrow tunnel that is largely sequestered from bulk solvent. In contrast, eukaryotic (Brassica juncea) HMGCS binds hymeglusin in a more solvent-exposed cavity.
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Miziorko HM, Skaff DA, Ramyar KX, McWhorter WJ, Geisbrecht BV. Hymeglusin inhibition of bacterial hydroxymethylglutaryl‐ CoA synthase (mvaS). FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.964.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Henry M Miziorko
- Molecular Biology & BiochemistryUniversity of Missouri-Kansas CityKansas CityMO
| | - D Andrew Skaff
- Molecular Biology & BiochemistryUniversity of Missouri-Kansas CityKansas CityMO
| | - Kasra X Ramyar
- Cell Biology & BiophysicsUniversity of Missouri-Kansas CityKansas CityMO
| | | | - Brian V Geisbrecht
- Cell Biology & BiophysicsUniversity of Missouri-Kansas CityKansas CityMO
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Garcia BL, Summers BJ, Lin Z, Ramyar KX, Ricklin D, Kamath DV, Fu ZQ, Lambris JD, Geisbrecht BV. Diversity in the C3b contact residues and tertiary structures of the staphylococcal complement inhibitor (SCIN) protein family. J Biol Chem 2012. [DOI: 10.1074/jbc.a111.298984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Garcia BL, Ramyar KX, Ricklin D, Lambris JD, Geisbrecht BV. Advances in understanding the structure, function, and mechanism of the SCIN and Efb families of Staphylococcal immune evasion proteins. Adv Exp Med Biol 2012; 946:113-33. [PMID: 21948365 DOI: 10.1007/978-1-4614-0106-3_7] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Our understanding of both the nature and diversity of Staphylococcal immune evasion proteins has increased tremendously throughout the last several years. Among this group of molecules, members of the SCIN and Efb families of complement inhibitors have been the subject of particularly intense study. This work has demonstrated that both types of proteins exert their primary function by inhibiting C3 convertases, which lie at the heart of the complement-mediated immune response. Despite this similarity, however, significant differences in structure/function relationships and mechanisms of action exist between these bacterial proteins. Furthermore, divergent secondary effects on host immune responses have also been described for these two protein families. This chapter summarizes recent advances toward understanding the structure, function, and mechanism of the SCIN and Efb families, and suggests potential directions for the field over the coming years.
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Affiliation(s)
- Brandon L Garcia
- School of Biological Sciences, University of Missouri, Kansas City, MO 64110, USA.
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Garcia BL, Summers BJ, Lin Z, Ramyar KX, Ricklin D, Kamath DV, Fu ZQ, Lambris JD, Geisbrecht BV. Diversity in the C3b [corrected] contact residues and tertiary structures of the staphylococcal complement inhibitor (SCIN) protein family. J Biol Chem 2011; 287:628-640. [PMID: 22086928 DOI: 10.1074/jbc.m111.298984] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To survive in immune-competent hosts, the pathogen Staphylococcus aureus expresses and secretes a sophisticated array of proteins that inhibit the complement system. Among these are the staphylococcal complement inhibitors (SCIN), which are composed of three active proteins (SCIN-A, -B, and -C) and one purportedly inactive member (SCIN-D or ORF-D). Because previous work has focused almost exclusively on SCIN-A, we sought to provide initial structure/function information on additional SCIN proteins. To this end we determined crystal structures of an active, N-terminal truncation mutant of SCIN-B (denoted SCIN-B18-85) both free and bound to the C3c fragment of complement component C3 at 1.5 and 3.4 Å resolution, respectively. Comparison of the C3c/SCIN-B18-85 structure with that of C3c/SCIN-A revealed that both proteins target the same functional hotspot on the C3b/C3c surface yet harbor diversity in both the type of residues and interactions formed at their C3b/C3c interfaces. Most importantly, these structures allowed identification of Arg44 and Tyr51 as residues key for SCIN-B binding to C3b and subsequent inhibition of the AP C3 convertase. In addition, we also solved several crystal structures of SCIN-D to 1.3 Å limiting resolution. This revealed an unexpected structural deviation in the N-terminal α helix relative to SCIN-A and SCIN-B. Comparative analysis of both electrostatic potentials and surface complementarity suggest a physical explanation for the inability of SCIN-D to bind C3b/C3c. Together, these studies provide a more thorough understanding of immune evasion by S. aureus and enhance potential use of SCIN proteins as templates for design of complement targeted therapeutics.
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Affiliation(s)
- Brandon L Garcia
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110
| | - Brady J Summers
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110
| | - Zhuoer Lin
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Kasra X Ramyar
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110
| | - Daniel Ricklin
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Divya V Kamath
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110
| | - Zheng-Qing Fu
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
| | - John D Lambris
- Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Brian V Geisbrecht
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110.
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Garcia BL, Tzekou A, Ricklin D, Ramyar KX, McWhorter WJ, Geisbrecht BV, Lambris JD. Molecular basis for complement recognition and inhibition by staphylococcal complement inhibitors. Mol Immunol 2010. [DOI: 10.1016/j.molimm.2010.05.145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Garcia BL, Ramyar KX, Tzekou A, Ricklin D, McWhorter WJ, Lambris JD, Geisbrecht BV. Molecular basis for complement recognition and inhibition determined by crystallographic studies of the staphylococcal complement inhibitor (SCIN) bound to C3c and C3b. J Mol Biol 2010; 402:17-29. [PMID: 20654625 DOI: 10.1016/j.jmb.2010.07.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 07/13/2010] [Accepted: 07/14/2010] [Indexed: 11/15/2022]
Abstract
The human complement system plays an essential role in innate and adaptive immunity by marking and eliminating microbial intruders. Activation of complement on foreign surfaces results in proteolytic cleavage of complement component 3 (C3) into the potent opsonin C3b, which triggers a variety of immune responses and participates in a self-amplification loop mediated by a multi-protein assembly known as the C3 convertase. The human pathogen Staphylococcus aureus has evolved a sophisticated and potent complement evasion strategy, which is predicated upon an arsenal of potent inhibitory proteins. One of these, the staphylococcal complement inhibitor (SCIN), acts at the level of the C3 convertase (C3bBb) and impairs downstream complement function by trapping the convertase in a stable but inactive state. Previously, we have shown that SCIN binds C3b directly and competitively inhibits binding of human factor H and, to a lesser degree, that of factor B to C3b. Here, we report the co-crystal structures of SCIN bound to C3b and C3c at 7.5 and 3.5 A limiting resolution, respectively, and show that SCIN binds a critical functional area on C3b. Most significantly, the SCIN binding site sterically occludes the binding sites of both factor H and factor B. Our results give insight into SCIN binding to activated derivatives of C3, explain how SCIN can recognize C3b in the absence of other complement components, and provide a structural basis for the competitive C3b-binding properties of SCIN. In the future, this may suggest templates for the design of novel complement inhibitors based upon the SCIN structure.
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Affiliation(s)
- Brandon L Garcia
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, MO 64110, USA
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Garcia BL, Tzekou A, Ramyar KX, McWhorter WJ, Ricklin D, Lambris JD, Geisbrecht BV. Crystallization of human complement component C3b in the presence of a staphylococcal complement-inhibitor protein (SCIN). Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:482-5. [PMID: 19407382 DOI: 10.1107/s174430910901207x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/31/2009] [Indexed: 11/10/2022]
Abstract
Staphylococcus aureus secretes a number of small proteins that effectively attenuate the human innate immune response. Among these, the staphylococcal complement-inhibitor protein (SCIN) disrupts the function of the complement component 3 (C3) convertase that is initiated through either the classical or the alternative pathway and thereby prevents amplification of the complement response on the bacterial surface. Recent studies have shown that SCIN may affect the activities of the C3 convertase by binding in an equimolar fashion to C3b, which is itself an integral although non-enzymatic component of the convertase. In order to better understand the nature of the C3b-SCIN interaction, the hanging-drop vapor-diffusion technique was used to crystallize human C3b in the presence of a recombinant form of SCIN. These crystals diffracted synchrotron X-rays to approximately 6 A Bragg spacing and grew in a primitive tetragonal space group (P4(1)2(1)2 or P4(3)2(1)2; unit-cell parameters a = b = 128.03, c = 468.59 A). Cell-content analysis of these crystals was consistent with the presence of either two 1:1 complexes or a single 2:2 assembly in the asymmetric unit, both of which correspond to a solvent content of 51.9%. By making use of these crystals, solution of the C3b-SCIN structure should further our understanding of complement inhibition and immune evasion by this pathogen.
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Hammel M, Sfyroera G, Pyrpassopoulos S, Ricklin D, Ramyar KX, Pop M, Jin Z, Lambris JD, Geisbrecht BV. Characterization of Ehp, a secreted complement inhibitory protein from Staphylococcus aureus. J Biol Chem 2007; 282:30051-61. [PMID: 17699522 DOI: 10.1074/jbc.m704247200] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We report here the discovery and characterization of Ehp, a new secreted Staphylococcus aureus protein that potently inhibits the alternative complement activation pathway. Ehp was identified through a genomic scan as an uncharacterized secreted protein from S. aureus, and immunoblotting of conditioned S. aureus culture medium revealed that the Ehp protein was secreted at the highest levels during log-phase bacterial growth. The mature Ehp polypeptide is composed of 80 residues and is 44% identical to the complement inhibitory domain of S. aureus Efb (extracellular fibrinogen-binding protein). We observed preferential binding by Ehp to native and hydrolyzed C3 relative to fully active C3b and found that Ehp formed a subnanomolar affinity complex with these various forms of C3 by binding to its thioester-containing C3d domain. Site-directed mutagenesis demonstrated that Arg(75) and Asn(82) are important in forming the Ehp.C3d complex, but loss of these side chains did not completely disrupt Ehp/C3d binding. This suggested the presence of a second C3d-binding site in Ehp, which was mapped to the proximity of Ehp Asn(63). Further molecular level details of the Ehp/C3d interaction were revealed by solving the 2.7-A crystal structure of an Ehp.C3d complex in which the low affinity site had been mutationally inactivated. Ehp potently inhibited C3b deposition onto sensitized surfaces by the alternative complement activation pathway. This inhibition was directly related to Ehp/C3d binding and was more potent than that seen for Efb-C. An altered conformation in Ehp-bound C3 was detected by monoclonal antibody C3-9, which is specific for a neoantigen exposed in activated forms of C3. Our results suggest that increased inhibitory potency of Ehp relative to Efb-C is derived from the second C3-binding site in this new protein.
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Affiliation(s)
- Michal Hammel
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
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21
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Lassen KG, Ramyar KX, Bailey JR, Zhou Y, Siliciano RF. Nuclear retention of multiply spliced HIV-1 RNA in resting CD4+ T cells. PLoS Pathog 2006; 2:e68. [PMID: 16839202 PMCID: PMC1487174 DOI: 10.1371/journal.ppat.0020068] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 05/25/2006] [Indexed: 01/01/2023] Open
Abstract
HIV-1 latency in resting CD4+ T cells represents a major barrier to virus eradication in patients on highly active antiretroviral therapy (HAART). We describe here a novel post-transcriptional block in HIV-1 gene expression in resting CD4+ T cells from patients on HAART. This block involves the aberrant localization of multiply spliced (MS) HIV-1 RNAs encoding the critical positive regulators Tat and Rev. Although these RNAs had no previously described export defect, we show that they exhibit strict nuclear localization in resting CD4+ T cells from patients on HAART. Overexpression of the transcriptional activator Tat from non-HIV vectors allowed virus production in these cells. Thus, the nuclear retention of MS HIV-1 RNA interrupts a positive feedback loop and contributes to the non-productive nature of infection of resting CD4+ T cells. To define the mechanism of nuclear retention, proteomic analysis was used to identify proteins that bind MS HIV-1 RNA. Polypyrimidine tract binding protein (PTB) was identified as an HIV-1 RNA-binding protein differentially expressed in resting and activated CD4+ T cells. Overexpression of PTB in resting CD4+ T cells from patients on HAART allowed cytoplasmic accumulation of HIV-1 RNAs. PTB overexpression also induced virus production by resting CD4+ T cells. Virus culture experiments showed that overexpression of PTB in resting CD4+ T cells from patients on HAART allowed release of replication-competent virus, while preserving a resting cellular phenotype. Whether through effects on RNA export or another mechanism, the ability of PTB to reverse latency without inducing cellular activation is a result with therapeutic implications.
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MESH Headings
- Acquired Immunodeficiency Syndrome/genetics
- Acquired Immunodeficiency Syndrome/physiopathology
- Antiretroviral Therapy, Highly Active
- CD4-Positive T-Lymphocytes/chemistry
- CD4-Positive T-Lymphocytes/physiology
- CD4-Positive T-Lymphocytes/virology
- Cell Nucleus/chemistry
- Cell Nucleus/physiology
- Cell Nucleus/virology
- Gene Expression Regulation, Viral
- Gene Products, rev/analysis
- Gene Products, rev/genetics
- Gene Products, rev/physiology
- Gene Products, tat/analysis
- Gene Products, tat/genetics
- Gene Products, tat/physiology
- HIV-1/genetics
- HIV-1/pathogenicity
- HIV-1/physiology
- Humans
- Lymphocyte Activation/genetics
- Lymphocyte Activation/physiology
- Polypyrimidine Tract-Binding Protein/analysis
- Polypyrimidine Tract-Binding Protein/genetics
- Polypyrimidine Tract-Binding Protein/physiology
- RNA Splicing
- RNA, Viral/analysis
- RNA, Viral/genetics
- Virus Latency/physiology
- Virus Replication/genetics
- Virus Replication/physiology
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Kara G Lassen
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Kasra X Ramyar
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Justin R Bailey
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Yan Zhou
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Robert F Siliciano
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Howard Hughes Medical Institute, Baltimore, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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Hammel M, Ramyar KX, Spencer CT, Geisbrecht BV. Crystallization and X-ray diffraction analysis of the complement component-3 (C3) inhibitory domain of Efb from Staphylococcus aureus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:285-8. [PMID: 16511324 PMCID: PMC2197172 DOI: 10.1107/s1744309106005926] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 02/17/2006] [Indexed: 11/10/2022]
Abstract
The extracellular fibrinogen-binding protein (Efb) of Staphylococcus aureus is a multifunctional virulence factor capable of potent inhibition of complement component-3 (C3) activity in addition to its previously described fibrinogen-binding properties. A truncated recombinant form of Efb (Efb-C) that binds C3 has been overexpressed and purified and has been crystallized using the hanging-drop vapor-diffusion technique. Crystals of native Efb-C grew in the tetragonal space group P4(3) (unit-cell parameters a = b = 59.53, c = 46.63 A) with two molecules in the asymmetric unit and diffracted well beyond 1.25 A limiting Bragg spacing. To facilitate de novo phasing of the Efb-C crystals, two independent site-directed mutants were engineered in which either residue Ile112 or Val140 was replaced with methionine and crystals isomorphous to those of native Efb-C were reproduced using a seleno-L-methionine-labeled form of each mutant protein. Multiwavelength anomalous diffraction (MAD) data were collected on both mutants and analyzed for their phasing power toward solution and refinement of a high-resolution Efb-C crystal structure.
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Affiliation(s)
- Michal Hammel
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri–Kansas City, USA
| | - Kasra X. Ramyar
- Division of Rheumatology, Department of Medicine, The Johns Hopkins University School of Medicine, USA
| | - Charles T. Spencer
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri–Kansas City, USA
| | - Brian V. Geisbrecht
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri–Kansas City, USA
- Correspondence e-mail:
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Lassen KG, Ramyar KX, Bailey JR, Zhou Y, Siliciano RF. A Novel Post-transcriptional Block in Gene Expression Contributes to HIV-1 Latency In Vivo. Retrovirology 2005. [DOI: 10.1186/1742-4690-2-s1-s74] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Cho HS, Mason K, Ramyar KX, Stanley AM, Gabelli SB, Denney DW, Leahy DJ. Structure of the extracellular region of HER2 alone and in complex with the Herceptin Fab. Nature 2003; 421:756-60. [PMID: 12610629 DOI: 10.1038/nature01392] [Citation(s) in RCA: 1091] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2002] [Accepted: 12/17/2002] [Indexed: 12/13/2022]
Abstract
HER2 (also known as Neu, ErbB2) is a member of the epidermal growth factor receptor (EGFR; also known as ErbB) family of receptor tyrosine kinases, which in humans includes HER1 (EGFR, ERBB1), HER2, HER3 (ERBB3) and HER4 (ERBB4). ErbB receptors are essential mediators of cell proliferation and differentiation in the developing embryo and in adult tissues, and their inappropriate activation is associated with the development and severity of many cancers. Overexpression of HER2 is found in 20-30% of human breast cancers, and correlates with more aggressive tumours and a poorer prognosis. Anticancer therapies targeting ErbB receptors have shown promise, and a monoclonal antibody against HER2, Herceptin (also known as trastuzumab), is currently in use as a treatment for breast cancer. Here we report crystal structures of the entire extracellular regions of rat HER2 at 2.4 A and human HER2 complexed with the Herceptin antigen-binding fragment (Fab) at 2.5 A. These structures reveal a fixed conformation for HER2 that resembles a ligand-activated state, and show HER2 poised to interact with other ErbB receptors in the absence of direct ligand binding. Herceptin binds to the juxtamembrane region of HER2, identifying this site as a target for anticancer therapies.
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MESH Headings
- Animals
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal, Humanized
- Binding Sites
- Binding Sites, Antibody
- Crystallography, X-Ray
- Humans
- Immunoglobulin Fab Fragments/chemistry
- Immunoglobulin Fab Fragments/immunology
- Ligands
- Models, Molecular
- Protein Structure, Tertiary
- Rats
- Receptor, ErbB-2/chemistry
- Receptor, ErbB-2/immunology
- Trastuzumab
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Affiliation(s)
- Hyun-Soo Cho
- Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205, USA
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Leahy DJ, Dann CE, Longo P, Perman B, Ramyar KX. A mammalian expression vector for expression and purification of secreted proteins for structural studies. Protein Expr Purif 2000; 20:500-6. [PMID: 11087690 DOI: 10.1006/prep.2000.1331] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A mammalian expression vector with features optimized for simple expression and purification of secreted proteins has been developed. This vector was constructed to facilitate X-ray crystallographic studies of cysteine-rich glycoproteins that are difficult to express by other means. Proteins expressed with this vector possess an N-terminal human growth hormone domain and an octahistidine tag separated from the desired polypeptide sequences by a tobacco etch virus protease recognition site. Advantages of this vector are high levels of expression, simple detection and purification of expressed proteins, and reliable cleavage of the fusion protein. Cotransfection of this vector with a dihydrofolate reductase gene allows amplification of expression levels with methotrexate. Over one dozen cysteine-rich secreted proteins have been expressed in sufficient quantity for structural studies using this vector; the structure of at least one of these proteins has been determined.
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Affiliation(s)
- D J Leahy
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205, USA
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