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Jin M, Huo D, Sun J, Hu J, Liu S, Zhan M, Zhang BZ, Huang JD. Enhancing immune responses of ESC-based TAA cancer vaccines with a novel OMV delivery system. J Nanobiotechnology 2024; 22:15. [PMID: 38166929 PMCID: PMC10763241 DOI: 10.1186/s12951-023-02273-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
Embryonic stem cell (ESC)-derived epitopes can act as therapeutic tumor vaccines against different types of tumors Jin (Adv Healthc Mater 2023). However, these epitopes have poor immunogenicity and stimulate insufficient CD8+ T cell responses, which motivated us to develop a new method to deliver and enhance their effectiveness. Bacterial outer membrane vesicles (OMVs) can serve as immunoadjuvants and act as a delivery vector for tumor antigens. In the current study, we engineered a new OMV platform for the co-delivery of ESC-derived tumor antigens and immune checkpoint inhibitors (PD-L1 antibody). An engineered Staphylococcal Protein A (SpA) was created to non-specifically bind to anti-PD-L1 antibody. SpyCatcher (SpC) and SpA were fused into the cell outer membrane protein OmpA to capture SpyTag-attached peptides and PD-L1 antibody, respectively. The modified OMV was able to efficiently conjugate with ESC-derived TAAs and PD-L1 antibody (SpC-OMVs + SpT-peptides + anti-PD-L1), increasing the residence time of TAAs in the body. The results showed that the combination therapy of ESC-based TAAs and PD-L1 antibody delivered by OMV had significant inhibitory effects in mouse tumor model. Specifically, it was effective in reducing tumor growth by enhancing IFN-γ-CD8+ T cell responses and increasing the number of CD8+ memory cells and antigen-specific T cells. Overall, the new OMV delivery system is a versatile platform that can enhance the immune responses of ESC-based TAA cancer vaccines.
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Affiliation(s)
- Meiling Jin
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | - Da Huo
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | - Jingjing Sun
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | | | - Shuzhen Liu
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | - Mingshuo Zhan
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | - Bao-Zhong Zhang
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China
| | - Jian-Dong Huang
- Chinese Academy of Sciences (CAS) Key Laboratory of Quantitative Engineering Biology, Shenzhen Institutes of Advanced Technology, Shenzhen Institute of Synthetic Biology, Chinese Academy of Sciences, Shenzhen, China.
- School of Biomedical Sciences, Faculty of Medicine, Li Ka Shing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
- Department of Clinical Oncology, Shenzhen Key Laboratory for Cancer Metastasis and Personalized Therapy, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China.
- Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen University, Guangzhou, 510120, China.
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2
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Olshefsky A, Benasutti H, Sylvestre M, Butterfield GL, Rocklin GJ, Richardson C, Hicks DR, Lajoie MJ, Song K, Leaf E, Treichel C, Decarreau J, Ke S, Kher G, Carter L, Chamberlain JS, Baker D, King NP, Pun SH. In vivo selection of synthetic nucleocapsids for tissue targeting. Proc Natl Acad Sci U S A 2023; 120:e2306129120. [PMID: 37939083 PMCID: PMC10655225 DOI: 10.1073/pnas.2306129120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 09/21/2023] [Indexed: 11/10/2023] Open
Abstract
Controlling the biodistribution of protein- and nanoparticle-based therapeutic formulations remains challenging. In vivo library selection is an effective method for identifying constructs that exhibit desired distribution behavior; library variants can be selected based on their ability to localize to the tissue or compartment of interest despite complex physiological challenges. Here, we describe further development of an in vivo library selection platform based on self-assembling protein nanoparticles encapsulating their own mRNA genomes (synthetic nucleocapsids or synNCs). We tested two distinct libraries: a low-diversity library composed of synNC surface mutations (45 variants) and a high-diversity library composed of synNCs displaying miniproteins with binder-like properties (6.2 million variants). While we did not identify any variants from the low-diversity surface library that yielded therapeutically relevant changes in biodistribution, the high-diversity miniprotein display library yielded variants that shifted accumulation toward lungs or muscles in just two rounds of in vivo selection. Our approach should contribute to achieving specific tissue homing patterns and identifying targeting ligands for diseases of interest.
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Affiliation(s)
- Audrey Olshefsky
- Department of Bioengineering, University of Washington, Seattle, WA98195
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Halli Benasutti
- Department of Biochemistry, University of Washington, Seattle, WA98195
| | - Meilyn Sylvestre
- Department of Bioengineering, University of Washington, Seattle, WA98195
| | - Gabriel L. Butterfield
- Institute for Protein Design, University of Washington, Seattle, WA98195
- Department of Molecular and Cellular Biology, University of Washington, Seattle, WA98195
| | - Gabriel J. Rocklin
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Christian Richardson
- Department of Bioengineering, University of Washington, Seattle, WA98195
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Derrick R. Hicks
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Marc J. Lajoie
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Kefan Song
- Department of Bioengineering, University of Washington, Seattle, WA98195
| | - Elizabeth Leaf
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Catherine Treichel
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Justin Decarreau
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Sharon Ke
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Gargi Kher
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Lauren Carter
- Institute for Protein Design, University of Washington, Seattle, WA98195
| | - Jeffrey S. Chamberlain
- Department of Biochemistry, University of Washington, Seattle, WA98195
- Department of Neurology, University of Washington, Seattle, WA98195
| | - David Baker
- Institute for Protein Design, University of Washington, Seattle, WA98195
- Department of Biochemistry, University of Washington, Seattle, WA98195
| | - Neil P. King
- Institute for Protein Design, University of Washington, Seattle, WA98195
- Department of Biochemistry, University of Washington, Seattle, WA98195
| | - Suzie H. Pun
- Department of Bioengineering, University of Washington, Seattle, WA98195
- Molecular Engineering and Sciences Institute, University of Washington, Seattle, WA98195
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3
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Young PG, Paynter JM, Wardega JK, Middleditch MJ, Payne LS, Baker EN, Squire CJ. Domain structure and cross-linking in a giant adhesin from the Mobiluncus mulieris bacterium. Acta Crystallogr D Struct Biol 2023; 79:971-979. [PMID: 37860959 PMCID: PMC10619420 DOI: 10.1107/s2059798323007507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/27/2023] [Indexed: 10/21/2023] Open
Abstract
Cell-surface proteins known as adhesins enable bacteria to colonize particular environments, and in Gram-positive bacteria often contain autocatalytically formed covalent intramolecular cross-links. While investigating the prevalence of such cross-links, a remarkable example was discovered in Mobiluncus mulieris, a pathogen associated with bacterial vaginosis. This organism encodes a putative adhesin of 7651 residues. Crystallography and mass spectrometry of two selected domains, and AlphaFold structure prediction of the remainder of the protein, were used to show that this adhesin belongs to the family of thioester, isopeptide and ester-bond-containing proteins (TIE proteins). It has an N-terminal domain homologous to thioester adhesion domains, followed by 51 immunoglobulin (Ig)-like domains containing ester- or isopeptide-bond cross-links. The energetic cost to the M. mulieris bacterium in retaining such a large adhesin as a single gene or protein construct suggests a critical role in pathogenicity and/or persistence.
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Affiliation(s)
- Paul G. Young
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, c/o The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Jacob M. Paynter
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Julia K. Wardega
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Martin J. Middleditch
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Leo S. Payne
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Edward N. Baker
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, c/o The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Christopher J. Squire
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, c/o The University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
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4
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Ma Q, Lei H, Cao Y. Intramolecular covalent bonds in Gram-positive bacterial surface proteins. Chembiochem 2022; 23:e202200316. [PMID: 35801833 DOI: 10.1002/cbic.202200316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/07/2022] [Indexed: 11/09/2022]
Abstract
Gram-positive bacteria experience considerable mechanical perturbation when adhering to host surfaces during colonization and infection. They have evolved various adhesion proteins that are mechanically robust to ensure strong surface adhesion. Recently, it was discovered that these adhesion proteins contain rare, extra intramolecular covalent bonds that stabilize protein structures and participate in surface bonding. These intramolecular covalent bonds include isopeptides, thioesters, and ester bonds, which often form spontaneously without the need for additional enzymes. With the development of single-molecule force spectroscopy techniques, the detailed mechanical roles of these intramolecular covalent bonds have been revealed. In this review, we summarize the recent advances in this area of research, focusing on the link between the mechanical stability and function of these covalent bonds in Gram-positive bacterial surface proteins. We also highlight the potential impact of these discoveries on the development of novel antibiotics and chemical biology tools.
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Affiliation(s)
- Quan Ma
- Nanjing University, Department of Physics, CHINA
| | - Hai Lei
- Nanjing University, Department of Physics, CHINA
| | - Yi Cao
- Nanjing University, Department of Physics, 22 Hankou Road, 210093, Nanjing, CHINA
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5
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Lei H, Ma Q, Li W, Wen J, Ma H, Qin M, Wang W, Cao Y. An ester bond underlies the mechanical strength of a pathogen surface protein. Nat Commun 2021; 12:5082. [PMID: 34426584 PMCID: PMC8382745 DOI: 10.1038/s41467-021-25425-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 08/10/2021] [Indexed: 11/23/2022] Open
Abstract
Gram-positive bacteria can resist large mechanical perturbations during their invasion and colonization by secreting various surface proteins with intramolecular isopeptide or ester bonds. Compared to isopeptide bonds, ester bonds are prone to hydrolysis. It remains elusive whether ester bonds can completely block mechanical extension similarly to isopeptide bonds, or whether ester bonds dissipate mechanical energy by bond rupture. Here, we show that an ester-bond containing stalk domain of Cpe0147 is inextensible even at forces > 2 nN. The ester bond locks the structure to a partially unfolded conformation, in which the ester bond remains largely water inaccessible. This allows the ester bond to withstand considerable mechanical forces and in turn prevent complete protein unfolding. However, the protecting effect might be reduced at non-physiological basic pHs or low calcium concentrations due to destabilizing the protein structures. Inspired by this design principle, we engineer a disulfide mutant resistant to mechanical unfolding under reducing conditions. Bacterial surface adhesion proteins are characterized by unusual mechanical properties. Here, the authors use atomic force microscopy-based technique to study a surface-anchoring protein Cpe0147 from Clostridium perfringens and show that an ester bond can withstand considerable mechanical forces and prevent complete protein unfolding.
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Affiliation(s)
- Hai Lei
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China.,Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing, China
| | - Quan Ma
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China
| | - Wenfei Li
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China
| | - Jing Wen
- Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing, China
| | - Haibo Ma
- Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing, China
| | - Meng Qin
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China
| | - Wei Wang
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China
| | - Yi Cao
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, China. .,Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing, China.
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6
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Structure-function characterization of Streptococcus intermedius surface antigen Pas. J Bacteriol 2021; 203:e0017521. [PMID: 34339301 DOI: 10.1128/jb.00175-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus intermedius, an oral commensal bacterium, is found at various sites including subgingival dental plaque, purulent infections, and in cystic fibrosis lungs. Oral streptococci utilize proteins on their surface to adhere to tissues and/or surfaces localizing the bacteria, which subsequently leads to the development of biofilms, colonization and infection. Among the 19 genomically annotated cell-wall attached surface proteins on S. intermedius, Pas is an adhesin that belongs to the Antigen I/II (AgI/II) family. Here we have structurally and functionally characterized Pas, particularly focusing on its microbial-host as well as microbial-microbial interactions. The crystal structures of VPas and C123Pas show high similarity with AgI/II of S. mutans. VPas hosts a conserved metal binding site, and likewise the C123Pas structure retains its conserved metal binding sites and isopeptide bonds within its three DEv-IgG domains. Pas interacts with nanomolar affinity to lung alveolar glycoprotein 340 (Gp340), its scavenger receptor cysteine rich domains (SRCRs) and with fibrinogen. Both Candida albicans and Pseudomonas aeruginosa, the opportunistic pathogens that cohabitate with S. intermedius in the lungs of CFTR patients were studied in dual-species biofilm studies. The Pas deficient mutant (Δpas) displayed significant reduction in dual biofilm formation with C. albicans. In similar studies with P. aeruginosa, Pas did not mediate the biofilm formation with either the acute isolate (PAO1), or the chronic isolate (FRD1). However, the Sortase A deficient mutant (ΔsrtA) displayed reduced biofilm formation with both C. albicans and P. aeruginosa FRD1. Taken together, our findings highlight the role of Pas in both microbial-host and interkingdom interactions and expose its potential role in disease outcomes. Importance Streptococcus intermedius, an oral commensal bacterium, has been clinically observed in subgingival dental plaque, purulent infections, and in cystic fibrosis lungs. In this study, we have (a) determined the crystal structure of the V- and C-regions of Pas; (b) shown that its surface protein Pas adheres to fibrinogen, which could potentially ferry the microbe through the blood stream from the oral cavity; (c) characterized Pas's high affinity adherence to lung alveolar protein Gp340 that could fixate the microbe on lung epithelial cells; and (d) most importantly shown that these surface proteins on the oral commensal S. intermedius enhances biofilms of known pathogens Candida albicans and Pseudomonas aeruginosa.
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Gago-Córdoba C, Val-Calvo J, Abia D, Díaz-Talavera A, Miguel-Arribas A, Aguilar Suárez R, van Dijl JM, Wu LJ, Meijer WJJ. A Conserved Class II Type Thioester Domain-Containing Adhesin Is Required for Efficient Conjugation in Bacillus subtilis. mBio 2021; 12:e00104-21. [PMID: 33727345 PMCID: PMC8092201 DOI: 10.1128/mbio.00104-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/05/2021] [Indexed: 12/16/2022] Open
Abstract
Conjugation, the process by which a DNA element is transferred from a donor to a recipient cell, is the main horizontal gene transfer route responsible for the spread of antibiotic resistance and virulence genes. Contact between a donor and a recipient cell is a prerequisite for conjugation, because conjugative DNA is transferred into the recipient via a channel connecting the two cells. Conjugative elements encode proteins dedicated to facilitating the recognition and attachment to recipient cells, also known as mating pair formation. A subgroup of the conjugative elements is able to mediate efficient conjugation during planktonic growth, and mechanisms facilitating mating pair formation will be particularly important in these cases. Conjugative elements of Gram-negative bacteria encode conjugative pili, also known as sex pili, some of which are retractile. Far less is known about mechanisms that promote mating pair formation in Gram-positive bacteria. The conjugative plasmid pLS20 of the Gram-positive bacterium Bacillus subtilis allows efficient conjugation in liquid medium. Here, we report the identification of an adhesin gene in the pLS20 conjugation operon. The N-terminal region of the adhesin contains a class II type thioester domain (TED) that is essential for efficient conjugation, particularly in liquid medium. We show that TED-containing adhesins are widely conserved in Gram-positive bacteria, including pathogens where they often play crucial roles in pathogenesis. Our study is the first to demonstrate the involvement of a class II type TED-containing adhesin in conjugation.IMPORTANCE Bacterial resistance to antibiotics has become a serious health care problem. The spread of antibiotic resistance genes between bacteria of the same or different species is often mediated by a process named conjugation, where a donor cell transfers DNA to a recipient cell through a connecting channel. The first step in conjugation is recognition and attachment of the donor to a recipient cell. Little is known about this first step, particularly in Gram-positive bacteria. Here, we show that the conjugative plasmid pLS20 of Bacillus subtilis encodes an adhesin protein that is essential for effective conjugation. This adhesin protein has a structural organization similar to adhesins produced by other Gram-positive bacteria, including major pathogens, where the adhesins serve in attachment to host tissues during colonization and infection. Our findings may thus also open novel avenues to design drugs that inhibit the spread of antibiotic resistance by blocking the first recipient-attachment step in conjugation.
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Affiliation(s)
- César Gago-Córdoba
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
| | - Jorge Val-Calvo
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
| | - David Abia
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
| | - Alberto Díaz-Talavera
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
| | - Andrés Miguel-Arribas
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
| | - Rocío Aguilar Suárez
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Jan Maarten van Dijl
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Ling Juan Wu
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Wilfried J J Meijer
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Madrid, Spain
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Abstract
Intramolecular isopeptide bonds, formed autocatalytically between Lys and Asn/Asp side chains, are widely present in the immunoglobulin-like domains of Gram-positive bacterial adhesins, including Group A Streptococcus, and confer considerable mechanical and chemical stability. These properties make them attractive for applications in biotechnology. Here, we detail the practical considerations that are involved in engineering isopeptide bonds into Ig-like proteins, including the choice of a site where bond-forming residues could be introduced and the appropriate methodology for mutagenesis. We specify how to determine whether an isopeptide bond has formed, what strategies can be adopted to overcome problems, and how to monitor the stability of the engineered protein.
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9
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Ness S, Hilleringmann M. Streptococcus pneumoniae Type 1 Pilus - A Multifunctional Tool for Optimized Host Interaction. Front Microbiol 2021; 12:615924. [PMID: 33633703 PMCID: PMC7899983 DOI: 10.3389/fmicb.2021.615924] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 01/20/2021] [Indexed: 11/13/2022] Open
Abstract
Streptococcus pneumoniae represents a major Gram-positive human pathogen causing bacterial pneumonia, otitis media, meningitis, and other invasive diseases. Several pneumococcal isolates show increasing resistance rates against antibacterial agents. A variety of virulence factors promote pneumococcal pathogenicity with varying importance in different stages of host infection. Virulence related hair-like structures ("pili") are complex, surface located protein arrays supporting proper host interaction. In the last two decades different types of pneumococcal pili have been identified: pilus-1 (P1) and pilus-2 (P2) are formed by the catalytic activity of sortases that covalently assemble secreted polypeptide pilin subunits in a defined order and finally anchor the resulting pilus in the peptidoglycan. Within the long pilus fiber the presence of intramolecular isopeptide bonds confer high stability to the sequentially arranged individual pilins. This mini review will focus on S. pneumoniae TIGR4 P1 molecular architecture, the subunits it builds and provides insights into P1 sortase-mediated assembly. The complex P1 architecture (anchor-/backbone-/tip-subunits) allows the specific interaction with various target structures facilitating different steps of colonization, invasion and spreading within the host. Optimized pilin subunit confirmation supports P1 function under physiological conditions. Finally, aspects of P1- host interplay are summarized, including recent insights into P1 mechanobiology, which have important implications for P1 mediated pathogenesis.
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Affiliation(s)
| | - Markus Hilleringmann
- FG Protein Biochemistry & Cellular Microbiology, Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Munich, Germany
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Dos Santos Morais R, El-Kirat-Chatel S, Burgain J, Simard B, Barrau S, Paris C, Borges F, Gaiani C. A Fast, Efficient and Easy to Implement Method to Purify Bacterial Pili From Lacticaseibacillus rhamnosus GG Based on Multimodal Chromatography. Front Microbiol 2020; 11:609880. [PMID: 33391233 PMCID: PMC7775309 DOI: 10.3389/fmicb.2020.609880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/24/2020] [Indexed: 01/02/2023] Open
Abstract
Pili are polymeric proteins located at the cell surface of bacteria. These filamentous proteins play a pivotal role in bacterial adhesion with the surrounding environment. They are found both in Gram-negative and Gram-positive bacteria but differ in their structural organization. Purifying these high molecular weight proteins is challenging and has certainly slowed down their characterization. Here, we propose a chromatography-based protocol, mainly relying on multimodal chromatography (core bead technology using Capto Core 700 resin), to purify sortase-dependent SpaCBA pili from the probiotic strain Lacticaseibacillus rhamnosus GG (LGG). Contrary to previously published methods, this purification protocol does not require specific antibodies nor complex laboratory equipment, including for the multimodal chromatography step, and provides high degree of protein purity. No other proteins were detectable by SDS-PAGE and the 260/280 nm ratio (∼0.6) of the UV spectrum confirmed the absence of any other co-purified macromolecules. One can obtain ∼50 μg of purified pili, starting from 1 L culture at OD600nm ≈ 1, in 2–3 working days. This simple protocol could be useful to numerous laboratories to purify pili from LGG easily. Therefore, the present work should boost specific studies dedicated to LGG SpaCBA pili and the characterization of the interactions occurring with their protein partners at the molecular level. Moreover, this straightforward purification process might be extended to the purification of sortase-dependant pili from other Gram-positive bacteria.
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Affiliation(s)
| | - Sofiane El-Kirat-Chatel
- Laboratoire de Chimie Physique et Microbiologie pour les Matériaux et l'Environnement (LCPME), UMR 7564, CNRS-Université de Lorraine, Nancy, France
| | - Jennifer Burgain
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France
| | - Blandine Simard
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France
| | - Sarah Barrau
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France
| | - Cédric Paris
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France
| | - Frédéric Borges
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France
| | - Claire Gaiani
- Laboratoire d'Ingénierie des Biomolécules, Université de Lorraine, Nancy, France.,Institut Universitaire de France, Parris, France
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11
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Crystallization of Recombinant Fimbrial Proteins of Porphyromonas gingivalis. Methods Mol Biol 2020. [PMID: 32815130 DOI: 10.1007/978-1-0716-0939-2_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Porphyromonas gingivalis fimbriae play a critical role in colonization. Elucidation of the fimbrial structure in atomic detail is important for understanding the colonization mechanism and to provide means to combat periodontitis. X-ray crystallography is a technique that is used to obtain detailed information of proteins along with bound ligands and ions. Crystallization of the protein of interest is the first step toward structure determination. Unfortunately it is not possible to predict the crystallization condition of a certain protein or even if the protein can be crystallized. Protein crystallization is, on the contrary, a matter of trial and error. However, the best strategy for success is to focus on the protein purification step to obtain a sample that is pure, stable, homogeneous and of high concentration. This chapter addresses general methods for crystallization of fimbrial proteins.
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12
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Lynch MJ, Miller M, James M, Zhang S, Zhang K, Li C, Charon NW, Crane BR. Structure and chemistry of lysinoalanine crosslinking in the spirochaete flagella hook. Nat Chem Biol 2019; 15:959-965. [PMID: 31406373 PMCID: PMC6764852 DOI: 10.1038/s41589-019-0341-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 07/08/2019] [Indexed: 11/09/2022]
Abstract
The flagellar hook protein FlgE from spirochaete bacteria self-catalyzes the formation of an unusual inter-subunit lysinoalanine (Lal) crosslink that is critical for cell motility. Unlike other known examples of Lal biosynthesis, conserved cysteine and lysine residues in FlgE spontaneously react to form Lal without the involvement of additional enzymes. Oligomerization of FlgE via its D0 and Dc domains drives assembly of the crosslinking site at the D1-D2 domain interface. Structures of the FlgED2 domain, dehydroalanine (DHA) intermediate and Lal crosslinked FlgE subunits reveal successive snapshots of the reaction. Cys178 flips from a buried configuration to release hydrogen sulfide (H2S/HS-) and produce DHA. Interface residues provide hydrogen bonds to anchor the active site, facilitate β-elimination of Cys178 and polarize the peptide backbone to activate DHA for reaction with Lys165. Cysteine-reactive molecules accelerate DHA formation, whereas nucleophiles can intercept the DHA intermediate, thereby indicating a potential for Lal crosslink inhibitors to combat spirochaetal diseases.
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Affiliation(s)
- Michael J Lynch
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA
| | - Michael Miller
- Department of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
| | - Milinda James
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
| | - Sheng Zhang
- Proteomics Facility, Institute of Biotechnology, Cornell University, Ithaca, NY, USA
| | - Kai Zhang
- Philips Institute for Oral Health Research, Virginia Commonwealth University School of Dentistry, Richmond, VA, USA
| | - Chunhao Li
- Philips Institute for Oral Health Research, Virginia Commonwealth University School of Dentistry, Richmond, VA, USA
| | - Nyles W Charon
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.
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13
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Group A Streptococcus T Antigens Have a Highly Conserved Structure Concealed under a Heterogeneous Surface That Has Implications for Vaccine Design. Infect Immun 2019; 87:IAI.00205-19. [PMID: 30936156 DOI: 10.1128/iai.00205-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 03/25/2019] [Indexed: 12/20/2022] Open
Abstract
Group A Streptococcus (GAS) (Streptococcus pyogenes) is an important human pathogen associated with significant global morbidity and mortality for which there is no safe and efficacious vaccine. The T antigen, a protein that polymerizes to form the backbone of the GAS pilus structure, is a potential vaccine candidate. Previous surveys of the tee gene, which encodes the T antigen, have identified 21 different tee types and subtypes such that any T antigen-based vaccine must be multivalent and carefully designed to provide broad strain coverage. In this study, the crystal structures of three two-domain T antigens (T3.2, T13, and T18.1) were determined and found to have remarkable structural similarity to the previously reported T1 antigen, despite moderate overall sequence similarity. This has enabled reliable modeling of all major two-domain T antigens to reveal that T antigen sequence variation is distributed along the full length of the protein and shields a highly conserved core. Immunoassays performed with sera from immunized animals and commercial T-typing sera identified a significant cross-reactive antibody response between T18.1, T18.2, T3.2, and T13. The existence of shared epitopes between T antigens, combined with the remarkably conserved structure and high level of surface sequence divergence, has important implications for the design of multivalent T antigen-based vaccines.
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14
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Hatlem D, Trunk T, Linke D, Leo JC. Catching a SPY: Using the SpyCatcher-SpyTag and Related Systems for Labeling and Localizing Bacterial Proteins. Int J Mol Sci 2019; 20:E2129. [PMID: 31052154 PMCID: PMC6539128 DOI: 10.3390/ijms20092129] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 04/25/2019] [Accepted: 04/26/2019] [Indexed: 01/05/2023] Open
Abstract
The SpyCatcher-SpyTag system was developed seven years ago as a method for protein ligation. It is based on a modified domain from a Streptococcus pyogenes surface protein (SpyCatcher), which recognizes a cognate 13-amino-acid peptide (SpyTag). Upon recognition, the two form a covalent isopeptide bond between the side chains of a lysine in SpyCatcher and an aspartate in SpyTag. This technology has been used, among other applications, to create covalently stabilized multi-protein complexes, for modular vaccine production, and to label proteins (e.g., for microscopy). The SpyTag system is versatile as the tag is a short, unfolded peptide that can be genetically fused to exposed positions in target proteins; similarly, SpyCatcher can be fused to reporter proteins such as GFP, and to epitope or purification tags. Additionally, an orthogonal system called SnoopTag-SnoopCatcher has been developed from an S. pneumoniae pilin that can be combined with SpyCatcher-SpyTag to produce protein fusions with multiple components. Furthermore, tripartite applications have been produced from both systems allowing the fusion of two peptides by a separate, catalytically active protein unit, SpyLigase or SnoopLigase. Here, we review the current state of the SpyCatcher-SpyTag and related technologies, with a particular emphasis on their use in vaccine development and in determining outer membrane protein localization and topology of surface proteins in bacteria.
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Affiliation(s)
- Daniel Hatlem
- Bacterial Cell Surface Group, Section for Evolution and Genetics, Department of Biosciences, University of Oslo, 0316 Oslo, Norway.
| | - Thomas Trunk
- Bacterial Cell Surface Group, Section for Evolution and Genetics, Department of Biosciences, University of Oslo, 0316 Oslo, Norway.
| | - Dirk Linke
- Bacterial Cell Surface Group, Section for Evolution and Genetics, Department of Biosciences, University of Oslo, 0316 Oslo, Norway.
| | - Jack C Leo
- Bacterial Cell Surface Group, Section for Evolution and Genetics, Department of Biosciences, University of Oslo, 0316 Oslo, Norway.
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15
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Megta AK, Mishra AK, Palva A, von Ossowski I, Krishnan V. Crystal structure of basal pilin SpaE reveals the molecular basis of its incorporation in the lactobacillar SpaFED pilus. J Struct Biol 2019; 207:74-84. [PMID: 31026587 DOI: 10.1016/j.jsb.2019.04.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 04/15/2019] [Accepted: 04/23/2019] [Indexed: 11/16/2022]
Abstract
For some Gram-positive genera and species, the long-extended and adhesive sortase-dependent pilus plays an essential role during host colonization, biofilm formation, and immune modulation. Lactobacillus rhamnosus GG is a gut-adapted commensal strain that harbors the operonic genes for the SpaCBA and SpaFED pili, both being comprised of three different protein subunits termed the backbone, tip, and basal pilins. Crystal structures of the backbone pilins (SpaA and SpaD) have recently been solved, and here we describe the high-resolution (1.5 Å) structural determination of the SpaE basal pilin. SpaE consists of two immunoglobulin-like CnaB domains, with each displaying a spontaneously formed internal isopeptide bond, though apparently slow forming in the N-terminal domain. Remarkably, SpaE contains an atypically lengthy unstructured C-terminal tail, along with an YPKN pilin motif peptide, which is normally reserved for backbone subunits. Based on our analysis of the crystal structure data, we provide a molecular model for the basal positioning of the SpaE pilin within the SpaFED pilus.
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Affiliation(s)
- Abhin Kumar Megta
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana 121 001, India; School of Biotechnology, KIIT University, Odisha 751024, India
| | - Arjun K Mishra
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana 121 001, India
| | - Airi Palva
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | | | - Vengadesan Krishnan
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana 121 001, India.
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16
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von Ossowski I. Novel Molecular Insights about Lactobacillar Sortase-Dependent Piliation. Int J Mol Sci 2017; 18:ijms18071551. [PMID: 28718795 PMCID: PMC5536039 DOI: 10.3390/ijms18071551] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 07/11/2017] [Accepted: 07/14/2017] [Indexed: 01/09/2023] Open
Abstract
One of the more conspicuous structural features that punctuate the outer cell surface of certain bacterial Gram-positive genera and species is the sortase-dependent pilus. As these adhesive and variable-length protrusions jut outward from the cell, they provide a physically expedient and useful means for the initial contact between a bacterium and its ecological milieu. The sortase-dependent pilus displays an elongated macromolecular architecture consisting of two to three types of monomeric protein subunits (pilins), each with their own specific function and location, and that are joined together covalently by the transpeptidyl activity of a pilus-specific C-type sortase enzyme. Sortase-dependent pili were first detected among the Gram-positive pathogens and subsequently categorized as an essential virulence factor for host colonization and tissue invasion by these harmful bacteria. However, the sortase-dependent pilus was rebranded as also a niche-adaptation factor after it was revealed that “friendly” Gram-positive commensals exhibit the same kind of pilus structures, which includes two contrasting gut-adapted species from the Lactobacillus genus, allochthonous Lactobacillus rhamnosus and autochthonous Lactobacillus ruminis. This review will highlight and discuss what has been learned from the latest research carried out and published on these lactobacillar pilus types.
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Affiliation(s)
- Ingemar von Ossowski
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki FIN-00014, Finland.
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17
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Echelman DJ, Lee AQ, Fernández JM. Mechanical forces regulate the reactivity of a thioester bond in a bacterial adhesin. J Biol Chem 2017; 292:8988-8997. [PMID: 28348083 DOI: 10.1074/jbc.m117.777466] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/17/2017] [Indexed: 11/06/2022] Open
Abstract
Bacteria must withstand large mechanical shear forces when adhering to and colonizing hosts. Recent structural studies on a class of Gram-positive bacterial adhesins have revealed an intramolecular Cys-Gln thioester bond that can react with surface-associated ligands to covalently anchor to host surfaces. Two other examples of such internal thioester bonds occur in certain anti-proteases and in the immune complement system, both of which react with the ligand only after the thioester bond is exposed by a proteolytic cleavage. We hypothesized that mechanical forces in bacterial adhesion could regulate thioester reactivity to ligand analogously to such proteolytic gating. Studying the pilus tip adhesin Spy0125 of Streptococcus pyogenes, we developed a single molecule assay to unambiguously resolve the state of the thioester bond. We found that when Spy0125 was in a folded state, its thioester bond could be cleaved with the small-molecule nucleophiles methylamine and histamine, but when Spy0125 was mechanically unfolded and subjected to forces of 50-350 piconewtons, thioester cleavage was no longer observed. For folded Spy0125 without mechanical force exposure, thioester cleavage was in equilibrium with spontaneous thioester reformation, which occurred with a half-life of several minutes. Functionally, this equilibrium reactivity allows thioester-containing adhesins to sample potential substrates without irreversible cleavage and inactivation. We propose that such reversible thioester reactivity would circumvent potential soluble inhibitors, such as histamine released at sites of inflammation, and allow the bacterial adhesin to selectively associate with surface-bound ligands.
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Affiliation(s)
- Daniel J Echelman
- From the Department of Biological Sciences, Columbia University, New York, New York 10027
| | - Alex Q Lee
- From the Department of Biological Sciences, Columbia University, New York, New York 10027
| | - Julio M Fernández
- From the Department of Biological Sciences, Columbia University, New York, New York 10027
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18
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Bacterial physiology: The ties that bind. Nat Microbiol 2016; 1:16192. [PMID: 27670124 DOI: 10.1038/nmicrobiol.2016.192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Miller MR, Miller KA, Bian J, James ME, Zhang S, Lynch M, Callery PS, Hettick JM, Cockburn A, Liu J, Li C, Crane BR, Charon NW. Spirochaete flagella hook proteins self-catalyse a lysinoalanine covalent crosslink for motility. Nat Microbiol 2016; 1:16134. [PMID: 27670115 PMCID: PMC5077173 DOI: 10.1038/nmicrobiol.2016.134] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 07/06/2016] [Indexed: 12/25/2022]
Abstract
Spirochaetes are bacteria responsible for several serious diseases, including Lyme disease (Borrelia burgdorferi), syphilis (Treponema pallidum) and leptospirosis (Leptospira interrogans), and contribute to periodontal diseases (Treponema denticola)(1). These spirochaetes employ an unusual form of flagella-based motility necessary for pathogenicity; indeed, spirochaete flagella (periplasmic flagella) reside and rotate within the periplasmic space(2-11). The universal joint or hook that links the rotary motor to the filament is composed of ∼120-130 FlgE proteins, which in spirochaetes form an unusually stable, high-molecular-weight complex(9,12-17). In other bacteria, the hook can be readily dissociated by treatments such as heat(18). In contrast, spirochaete hooks are resistant to these treatments, and several lines of evidence indicate that the high-molecular-weight complex is the consequence of covalent crosslinking(12,13,17). Here, we show that T. denticola FlgE self-catalyses an interpeptide crosslinking reaction between conserved lysine and cysteine, resulting in the formation of an unusual lysinoalanine adduct that polymerizes the hook subunits. Lysinoalanine crosslinks are not needed for flagellar assembly, but they are required for cell motility and hence infection. The self-catalytic nature of FlgE crosslinking has important implications for protein engineering, and its sensitivity to chemical inhibitors provides a new avenue for the development of antimicrobials targeting spirochaetes.
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Affiliation(s)
- Michael R. Miller
- Department of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
| | - Kelly A. Miller
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
| | - Jiang Bian
- Department of Oral Biology, State University of New York, Buffalo, NY, 14214
| | - Milinda E. James
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
| | - Sheng Zhang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - Michael Lynch
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - Patrick S. Callery
- Department of Pharmaceutical Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
| | - Justin M. Hettick
- National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown WV 26505
| | - Andrew Cockburn
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
| | - Jun Liu
- Department of Pathology and Laboratory Medicine, University of Texas Health Sciences Center, Houston, TX, 77030
| | - Chunhao Li
- Department of Oral Biology, State University of New York, Buffalo, NY, 14214
| | - Brian R. Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - Nyles W. Charon
- Department of Microbiology, Immunology, and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506
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20
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Chaurasia P, Pratap S, von Ossowski I, Palva A, Krishnan V. New insights about pilus formation in gut-adapted Lactobacillus rhamnosus GG from the crystal structure of the SpaA backbone-pilin subunit. Sci Rep 2016; 6:28664. [PMID: 27349405 PMCID: PMC4923907 DOI: 10.1038/srep28664] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 06/08/2016] [Indexed: 12/11/2022] Open
Abstract
Thus far, all solved structures of pilin-proteins comprising sortase-assembled pili are from pathogenic genera and species. Here, we present the first crystal structure of a pilin subunit (SpaA) from a non-pathogen host (Lactobacillus rhamnosus GG). SpaA consists of two tandem CnaB-type domains, each with an isopeptide bond and E-box motif. Intriguingly, while the isopeptide bond in the N-terminal domain forms between lysine and asparagine, the one in the C-terminal domain atypically involves aspartate. We also solved crystal structures of mutant proteins where residues implicated in forming isopeptide bonds were replaced. Expectedly, the E-box-substituted E139A mutant lacks an isopeptide bond in the N-terminal domain. However, the C-terminal E269A substitution gave two structures; one of both domains with their isopeptide bonds present, and another of only the N-terminal domain, but with an unformed isopeptide bond and significant conformational changes. This latter crystal structure has never been observed for any other Gram-positive pilin. Notably, the C-terminal isopeptide bond still forms in D295N-substituted SpaA, irrespective of E269 being present or absent. Although E-box mutations affect SpaA proteolytic and thermal stability, a cumulative effect perturbing normal pilus polymerization was unobserved. A model showing the polymerized arrangement of SpaA within the SpaCBA pilus is proposed.
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Affiliation(s)
- Priyanka Chaurasia
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad-121 001, India.,Department of Biotechnology, Manipal University, Karnataka, 576104, India
| | - Shivendra Pratap
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad-121 001, India
| | | | - Airi Palva
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Vengadesan Krishnan
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad-121 001, India
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21
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Isopeptide bond in collagen- and fibrinogen-binding MSCRAMMs. Biophys Rev 2016; 8:75-83. [PMID: 28510145 DOI: 10.1007/s12551-015-0191-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 12/14/2015] [Indexed: 10/22/2022] Open
Abstract
The internal isopeptide bonds are amide bonds formed autocatalytically between the side chains of Lys and Asn/Asp residues and have been discovered recently. These bonds are well conserved in Gram-positive bacterial pilin proteins and are also observed over a wide range of Gram-positive bacterial surface proteins. The presence of these bonds confers the pilus subunits with remarkable properties in terms of thermal stability and resistance to proteases. Like pili, microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) are also surface proteins found only in Gram-positive bacteria. They specifically interact with the extracellular matrix (ECM) molecules like collagen, fibrinogen, fibronectin, laminin, etc. Many biophysical and biochemical studies have been carried out to characterize the isopeptide bonds in pili proteins from Gram-positive bacteria, but no attempts have been made to study the isopeptide bonds in MSCRAMMs. This short review aims to study the significance of the isopeptide bonds in relation to their function, by analyzing the crystal structures of collagen- and fibrinogen-binding MSCRAMMs. In this analysis, interestingly, we observed that the putative isopeptide bonds are restricted to the collagen-binding MSCRAMMs. Based on analogy with bacterial pilus subunits, we hypothesize that the collagen-binding MSCRAMMs possessing putative isopeptide bonds exhibit similar structural properties, which could help the bacteria in colonizing the host and provide resistance against host-defense mechanisms.
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