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Prajapati A, Palva A, von Ossowski I, Krishnan V. The crystal structure of the N-terminal domain of the backbone pilin LrpA reveals a new closure-and-twist motion for assembling dynamic pili in Ligilactobacillus ruminis. Acta Crystallogr D Struct Biol 2024; 80:474-492. [PMID: 38935340 DOI: 10.1107/s2059798324005114] [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: 03/25/2024] [Accepted: 05/30/2024] [Indexed: 06/28/2024] Open
Abstract
Sortase-dependent pili are long surface appendages that mediate attachment, colonization and biofilm formation in certain genera and species of Gram-positive bacteria. Ligilactobacillus ruminis is an autochthonous gut commensal that relies on sortase-dependent LrpCBA pili for host adherence and persistence. X-ray crystal structure snapshots of the backbone pilin LrpA were captured in two atypical bent conformations leading to a zigzag morphology in the LrpCBA pilus structure. Small-angle X-ray scattering and structural analysis revealed that LrpA also adopts the typical linear conformation, resulting in an elongated pilus morphology. Various conformational analyses and biophysical experiments helped to demonstrate that a hinge region located at the end of the flexible N-terminal domain of LrpA facilitates a new closure-and-twist motion for assembling dynamic pili during the assembly process and host attachment. Further, the incongruent combination of flexible domain-driven conformational dynamics and rigid isopeptide bond-driven stability observed in the LrpCBA pilus might also extend to the sortase-dependent pili of other bacteria colonizing a host.
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Affiliation(s)
- Amar Prajapati
- Laboratory of Structural Microbiology, 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
- Laboratory of Structural Microbiology, Regional Centre for Biotechnology, NCR, Biotech Science Cluster, Faridabad 121 001, India
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2
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Kumar V, Murmu S, Krishnan V. Deciphering the substrate specificity of housekeeping sortase A and pilus-specific sortase C of probiotic bacterium Lactococcus lactis. Biochimie 2022; 200:140-152. [PMID: 35654243 DOI: 10.1016/j.biochi.2022.05.017] [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: 01/28/2022] [Revised: 04/25/2022] [Accepted: 05/26/2022] [Indexed: 11/02/2022]
Abstract
Several strains and species of lactic acid bacteria (LAB) are widely used in fermented foods, including dairy products and also as probiotics, because of their contribution to various health benefits in humans. Sortase enzymes decorate the bacterial cell wall with different surface proteins and pili for facilitating the interactions with host and environment for the colonization and beneficial effects. While the sortases and sortase anchored proteins from pathogens have been the prime focus of the research in the past, sortases from many non-pathogenic bacteria, including LAB strains, have attracted attention for their potential applications in vaccine delivery and other clinical interventions. Here, we report the purification and functional characterization of two sortases (housekeeping SrtA and pilus-specific SrtC) from a probiotic Lactococcus lactis. The purified sortases were found to be active against the putative LPXTG motif-based peptide substrates, albeit with differences. The in-silico analysis provides insights into the residues involved in substrate binding and specificity. Overall, this study sheds new light on the aspects of structure, substrate specificity, and function of sortases from non-pathogenic bacteria, which may have physiological ramifications as well as their applications in sortase-mediated protein bioconjugation.
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Affiliation(s)
- Vijay Kumar
- Laboratory of Structural Microbiology, Regional Centre for Biotechnology, NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurugram Expressway, Faridabad, 121001, Haryana (NCR Delhi), India
| | - Sumit Murmu
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India; Regional Centre for Biotechnology, NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurugram Expressway, Faridabad, 121001, Haryana (NCR Delhi), India
| | - Vengadesan Krishnan
- Laboratory of Structural Microbiology, Regional Centre for Biotechnology, NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurugram Expressway, Faridabad, 121001, Haryana (NCR Delhi), India.
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3
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Zhang D, Wang Z, Hu S, Lescar J, Tam JP, Liu CF. Vypal2: A Versatile Peptide Ligase for Precision Tailoring of Proteins. Int J Mol Sci 2021; 23:ijms23010458. [PMID: 35008882 PMCID: PMC8745061 DOI: 10.3390/ijms23010458] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 12/29/2021] [Accepted: 12/29/2021] [Indexed: 12/19/2022] Open
Abstract
The last two decades have seen an increasing demand for new protein-modification methods from the biotech industry and biomedical research communities. Owing to their mild aqueous reaction conditions, enzymatic methods based on the use of peptide ligases are particularly desirable. In this regard, the recently discovered peptidyl Asx-specific ligases (PALs) have emerged as powerful biotechnological tools in recent years. However, as a new class of peptide ligases, their scope and application remain underexplored. Herein, we report the use of a new PAL, VyPAL2, for a diverse range of protein modifications. We successfully showed that VyPAL2 was an efficient biocatalyst for protein labelling, inter-protein ligation, and protein cyclization. The labelled or cyclized protein ligands remained functionally active in binding to their target receptors. We also demonstrated on-cell labelling of protein ligands pre-bound to cellular receptors and cell-surface engineering via modifying a covalently anchored peptide substrate pre-installed on cell-surface glycans. Together, these examples firmly establish Asx-specific ligases, such as VyPAL2, as the biocatalysts of the future for site-specific protein modification, with a myriad of applications in basic research and drug discovery.
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4
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Complete Genome Sequence Analysis of Brevibacillus laterosporus Bl-zj Reflects its Potential Algicidal Response. Curr Microbiol 2021; 78:1409-1417. [DOI: 10.1007/s00284-021-02378-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 02/05/2021] [Indexed: 12/14/2022]
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5
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Si L, Li P, Liu X, Luo L. Chinese herb medicine against Sortase A catalyzed transformations, a key role in gram-positive bacterial infection progress. J Enzyme Inhib Med Chem 2016; 31:184-196. [PMID: 27162091 DOI: 10.1080/14756366.2016.1178639] [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] [Indexed: 02/07/2023] Open
Abstract
Many Gram-positive bacteria can anchor their surface proteins to the cell wall peptidoglycan covalently by a common mechanism with Sortase A (SrtA), thus escaping from the host's identification of immune cells. SrtA can complete this anchoring process by cleaving LPXTG motif conserved among these surface proteins and thus these proteins anchor on the cell wall. Moreover, those SrtA mutants lose this capability to anchor these relative proteins, with these bacteria no longer infectious. Therefore, SrtA inhibitors can be promising anti-infective agents to cure bacterial infections. Chinese herb medicines (CHMs) (chosen from Science Citation Index) have exhibited inhibition on SrtA of Gram-positive pathogens irreversibly or reversibly. In general, CHMs are likely to have important long-term impact as new antibacterial compounds and sought after by academia and the pharmaceutical industry. This review mainly focuses on SrtA inhibitors from CHMs and the potential inhibiting mechanism related to chemical structures of compounds in CHMs.
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Affiliation(s)
- Lifang Si
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Pan Li
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Xiong Liu
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Lixin Luo
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
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6
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Self-generated covalent cross-links in the cell-surface adhesins of Gram-positive bacteria. Biochem Soc Trans 2015; 43:787-94. [DOI: 10.1042/bst20150066] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The ability of bacteria to adhere to other cells or to surfaces depends on long, thin adhesive structures that are anchored to their cell walls. These structures include extended protein oligomers known as pili and single, multi-domain polypeptides, mostly based on multiple tandem Ig-like domains. Recent structural studies have revealed the widespread presence of covalent cross-links, not previously seen within proteins, which stabilize these domains. The cross-links discovered so far are either isopeptide bonds that link lysine side chains to the side chains of asparagine or aspartic acid residues or ester bonds between threonine and glutamine side chains. These bonds appear to be formed by spontaneous intramolecular reactions as the proteins fold and are strategically placed so as to impart considerable mechanical strength.
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7
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Schneewind O, Missiakas D. Sec-secretion and sortase-mediated anchoring of proteins in Gram-positive bacteria. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:1687-97. [PMID: 24269844 PMCID: PMC4031296 DOI: 10.1016/j.bbamcr.2013.11.009] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/01/2013] [Accepted: 11/13/2013] [Indexed: 01/17/2023]
Abstract
Signal peptide-driven secretion of precursor proteins directs polypeptides across the plasma membrane of bacteria. Two pathways, Sec- and SRP-dependent, converge at the SecYEG translocon to thread unfolded precursor proteins across the membrane, whereas folded preproteins are routed via the Tat secretion pathway. Gram-positive bacteria lack an outer membrane and are surrounded by a rigid layer of peptidoglycan. Interactions with their environment are mediated by proteins that are retained in the cell wall, often through covalent attachment to the peptidoglycan. In this review, we describe the mechanisms for both Sec-dependent secretion and sortase-dependent assembly of proteins in the envelope of Gram-positive bacteria. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Olaf Schneewind
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA.
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8
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An H, Douillard FP, Wang G, Zhai Z, Yang J, Song S, Cui J, Ren F, Luo Y, Zhang B, Hao Y. Integrated transcriptomic and proteomic analysis of the bile stress response in a centenarian-originated probiotic Bifidobacterium longum BBMN68. Mol Cell Proteomics 2014; 13:2558-72. [PMID: 24965555 DOI: 10.1074/mcp.m114.039156] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bifidobacteria are natural inhabitants of the human gastrointestinal tract and well known for their health-promoting effects. Tolerance to bile stress is crucial for bifidobacteria to survive in the colon and to exert their beneficial actions. In this work, RNA-Seq transcriptomic analysis complemented with proteomic analysis was used to investigate the cellular response to bile in Bifidobacterium longum BBMN68. The transcript levels of 236 genes were significantly changed (≥ threefold, p < 0.001) and 44 proteins were differentially abundant (≥1.6-fold, p < 0.01) in B. longum BBMN68 when exposed to 0.75 g l(-1) ox-bile. The hemolysin-like protein and bile efflux systems were significantly over produced, which might prevent bile adsorption and exclude bile, respectively. The cell membrane composition was modified probably by an increase of cyclopropane fatty acid and a decrease of transmembrane proteins, resulting in a cell membrane more impermeable to bile salts. Our hypothesis was later confirmed by surface hydrophobicity assay. The transcription of genes related to xylose utilization and bifid shunt were up-regulated, which increased the production of ATP and reducing equivalents to cope with bile-induced damages in a xylan-rich colon environment. Bile salts signal the B. longum BBMN68 to gut entrance and enhance the expression of esterase and sortase associated with adhesion and colonization in intestinal tract, which was supported by a fivefold increased adhesion ability to HT-29 cells by BBMN68 upon bile exposure. Notably, bacterial one-hybrid and EMSA assay revealed that the two-component system senX3-regX3 controlled the expression of pstS in bifidobacteria and the role of this target gene in bile resistance was further verified by heterologous expression in Lactococcus lactis. Taken altogether, this study established a model for global response mechanisms in B. longum to bile.
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Affiliation(s)
- Haoran An
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - François P Douillard
- §Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Guohong Wang
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Zhengyuan Zhai
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Jin Yang
- ¶Core Genomic Facility, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Shuhui Song
- ¶Core Genomic Facility, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jianyun Cui
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Fazheng Ren
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Yunbo Luo
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Bing Zhang
- ¶Core Genomic Facility, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yanling Hao
- From the ‡Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Municipality, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China;
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9
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Walden M, Crow A, Nelson MD, Banfield MJ. Intramolecular isopeptide but not internal thioester bonds confer proteolytic and significant thermal stability to the S. pyogenes pilus adhesin Spy0125. Proteins 2013; 82:517-27. [PMID: 24123467 PMCID: PMC4282584 DOI: 10.1002/prot.24420] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/29/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
Abstract
Streptococcus pyogenes and other Gram-positive bacterial pathogens present long macromolecular filaments known as pili on their surface that mediate adhesion and colonization. These pili are covalent polymers, assembled by sortases. Typically, they comprise a putative adhesin at their tip, a backbone subunit present in multiple copies and a basal subunit that is covalently anchored to the peptidoglycan layer of the cell surface. The crystal structures of pilin subunits revealed the presence of unusual covalent linkages in these proteins, including intramolecular isopeptide and internal thioester bonds. The intramolecular isopeptide bonds in backbone pilins are important for protein stability. Here, using both the wild-type protein and a set of mutants, we assessed the proteolytic and thermal stability of the S. pyogenes pilus tip adhesin Spy0125, in the presence and absence of its intramolecular isopeptide and internal thioester bonds. We also determined a crystal structure of the internal thioester bond variant Spy0125Cys426Ala. We find that mutations in the intramolecular isopeptide bonds compromise the stability of Spy0125. Using limited proteolysis and thermal denaturation assays, we could separate the contribution of each intramolecular isopeptide bond to Spy0125 stability. In contrast, mutation in the internal thioester bond had a lesser effect on protein stability and the crystal structure is essentially identical to wild type. This work suggests that the internal thioester in Spy0125, although having a minor contributory role, is not required for protein stability and must have a different primary function, most likely mediating a covalent interaction with host cell ligands. Proteins 2014; 82:517–527. © 2013 The Authors Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Miriam Walden
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, United Kingdom
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10
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Deng X, Tian Y, Niu Q, Xu X, Shi H, Zhang H, Liang L, Zhang K, Huang X. The ComP-ComA quorum system is essential for "Trojan horse" like pathogenesis in Bacillus nematocida. PLoS One 2013; 8:e76920. [PMID: 24130811 PMCID: PMC3793909 DOI: 10.1371/journal.pone.0076920] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 09/04/2013] [Indexed: 11/24/2022] Open
Abstract
Bacillus nematocida B16 has been shown to use “Trojan horse” mechanism in pathogenesis that has characteristics of “social” behavior. The ComP-ComA system, a conserved quorum sensing system in the genus Bacillus, functions in many physiological processes including competence development, lipopeptide antibiotic surfactin production, degradative enzyme production and even some unknown functions. Here we investigated the requirement of ComP-ComA system in B. nematocida B16 for its pathogenicity against nematodes. The ΔcomP mutant displayed deficiencies in attracting and killing nematodes, due to the absence of attractive signal molecules and the decreased expressions of virulence factors, respectively. Contrarily, a complemented comP mutant at least partially resumed its pathogenicity. Our data from transcriptional analysis further confirmed that this signaling system directly or indirectly regulated the expressions of two major virulence proteases in the infection of B. nematocida B16. Bioinformatics analyses from comparative genomics also suggested that the potential target genes of transcription factor ComA were involved in the processes such as the synthesis of attractants, production of extracellular degradative enzymes and sortase, secondary metabolites biosynthesis, regulation of transcription factors, mobility, as well as transporters, most of which were different from a saprophytic relative B. subtilis 168. Therefore, our investigation firstly revealed that the participation and necessity of ComP-ComA signaling system in bacterial pathogenesis.
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Affiliation(s)
- Xidan Deng
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, PR China
| | - Yunxia Tian
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
| | - Qiuhong Niu
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan, PR China
| | - Xiao’e Xu
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
| | - Hui Shi
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
| | - Hanbo Zhang
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
| | - Lianming Liang
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
| | - Keqin Zhang
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
- * E-mail: (KZ); (XH)
| | - Xiaowei Huang
- Laboratory for Conservation and Utilization of Bio-Resources and Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, PR China
- * E-mail: (KZ); (XH)
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11
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Structural basis for group B streptococcus pilus 1 sortases C regulation and specificity. PLoS One 2012; 7:e49048. [PMID: 23145064 PMCID: PMC3493515 DOI: 10.1371/journal.pone.0049048] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 10/03/2012] [Indexed: 11/19/2022] Open
Abstract
Gram-positive bacteria assemble pili through class C sortase enzymes specialized in polymerizing pilin subunits into covalently linked, high-molecular-weight, elongated structures. Here we report the crystal structures of two class C sortases (SrtC1 and SrtC2) from Group B Streptococcus (GBS) Pilus Island 1. The structures show that both sortases are comprised of two domains: an 8-stranded β-barrel catalytic core conserved among all sortase family members and a flexible N-terminal region made of two α-helices followed by a loop, known as the lid, which acts as a pseudo-substrate. In vitro experiments performed with recombinant SrtC enzymes lacking the N-terminal portion demonstrate that this region of the enzyme is dispensable for catalysis but may have key roles in substrate specificity and regulation. Moreover, in vitro FRET-based assays show that the LPXTG motif common to many sortase substrates is not the sole determinant of sortase C specificity during pilin protein recognition.
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12
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Hendrickx APA, Poor CB, Jureller JE, Budzik JM, He C, Schneewind O. Isopeptide bonds of the major pilin protein BcpA influence pilus structure and bundle formation on the surface of Bacillus cereus. Mol Microbiol 2012; 85:152-63. [PMID: 22624947 DOI: 10.1111/j.1365-2958.2012.08098.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Bacillus cereus strains elaborate pili on their surface using a mechanism of sortase-mediated cross-linking of major and minor pilus components. Here we used a combination of electron microscopy and atomic force microscopy to visualize these structures. Pili occur as single, double or higher order assemblies of filaments formed from monomers of the major pilin, BcpA, capped by the minor pilin, BcpB. Previous studies demonstrated that within assembled pili, four domains of BcpA - CNA(1), CNA(2), XNA and CNA(3) - each acquire intramolecular lysine-asparagine isopeptide bonds formed via catalytic glutamic acid or aspartic acid residues. Here we showed that mutants unable to form the intramolecular isopeptide bonds in the CNA(2) or CNA(3) domains retain the ability to form pilus bundles. A mutant lacking the CNA(1) isopeptide bond assembled deformed pilin subunits that failed to associate as bundles. X-ray crystallography revealed that the BcpA variant Asp(312) Ala, lacking an aspartyl catalyst, did not generate the isopeptide bond within the jelly-roll structure of XNA. The Asp(312) Ala mutant was also unable to form bundles and promoted the assembly of deformed pili. Thus, structural integrity of the CNA(1) and XNA domains are determinants for the association of pili into higher order bundle structures and determine native pilus structure.
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13
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Schneewind O, Missiakas DM. Protein secretion and surface display in Gram-positive bacteria. Philos Trans R Soc Lond B Biol Sci 2012; 367:1123-39. [PMID: 22411983 PMCID: PMC3297441 DOI: 10.1098/rstb.2011.0210] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The cell wall peptidoglycan of Gram-positive bacteria functions as a surface organelle for the transport and assembly of proteins that interact with the environment, in particular, the tissues of an infected host. Signal peptide-bearing precursor proteins are secreted across the plasma membrane of Gram-positive bacteria. Some precursors carry C-terminal sorting signals with unique sequence motifs that are cleaved by sortase enzymes and linked to the cell wall peptidoglycan of vegetative forms or spores. The sorting signals of pilin precursors are cleaved by pilus-specific sortases, which generate covalent bonds between proteins leading to the assembly of fimbrial structures. Other precursors harbour surface (S)-layer homology domains (SLH), which fold into a three-pronged spindle structure and bind secondary cell wall polysaccharides, thereby associating with the surface of specific Gram-positive microbes. Type VII secretion is a non-canonical secretion pathway for WXG100 family proteins in mycobacteria. Gram-positive bacteria also secrete WXG100 proteins and carry unique genes that either contribute to discrete steps in secretion or represent distinctive substrates for protein transport reactions.
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Affiliation(s)
- Olaf Schneewind
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
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14
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Structure of the full-length major pilin from Streptococcus pneumoniae: implications for isopeptide bond formation in gram-positive bacterial pili. PLoS One 2011; 6:e22095. [PMID: 21760959 PMCID: PMC3132780 DOI: 10.1371/journal.pone.0022095] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 06/15/2011] [Indexed: 11/19/2022] Open
Abstract
The surface of the pneumococcal cell is adorned with virulence factors including pili. The major pilin RrgB, which forms the pilus shaft on pathogenic Streptococcus pneumoniae, comprises four immunoglobulin (Ig)-like domains, each with a common CnaB topology. The three C-terminal domains are each stabilized by internal Lys-Asn isopeptide bonds, formed autocatalytically with the aid of an essential Glu residue. The structure and orientation of the crucial N-terminal domain, which provides the covalent linkage to the next pilin subunit in the shaft, however, remain incompletely characterised. We report the crystal structure of full length RrgB, solved by X-ray crystallography at 2.8 Å resolution. The N-terminal (D1) domain makes few contacts with the rest of the RrgB structure, and has higher B-factors. This may explain why D1 is readily lost by proteolysis, as are the N-terminal domains of many major pilins. D1 is also found to have a triad of Lys, Asn and Glu residues in the same topological positions as in the other domains, yet mass spectrometry and the crystal structure show that no internal isopeptide bond is formed. We show that this is because β-strand G of D1, which carries the Asn residue, diverges from β-strand A, carrying the Lys residue, such that these residues are too far apart for bond formation. Strand G also carries the YPKN motif that provides the essential Lys residue for the sortase-mediated intermolecular linkages along the pilus shaft. Interaction with the sortase and formation of the intermolecular linkage could result in a change in the orientation of this strand, explaining why isopeptide bond formation in the N-terminal domains of some major pilins appears to take place only upon assembly of the pili.
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15
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Linke C, Young PG, Kang HJ, Bunker RD, Middleditch MJ, Caradoc-Davies TT, Proft T, Baker EN. Crystal structure of the minor pilin FctB reveals determinants of Group A streptococcal pilus anchoring. J Biol Chem 2010; 285:20381-9. [PMID: 20427291 DOI: 10.1074/jbc.m109.089680] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell surface pili are polymeric protein assemblies that enable bacteria to adhere to surfaces and to specific host tissues. The pili expressed by Gram-positive bacteria constitute a unique paradigm in which sortase-mediated covalent linkages join successive pilin subunits like beads on a string. These pili are formed from two or three distinct types of pilin subunit, typically encoded in small gene clusters, often with their cognate sortases. In Group A streptococci (GAS), a major pilin forms the polymeric backbone, whereas two minor pilins are located at the tip and the base. Here, we report the 1.9-A resolution crystal structure of the GAS basal pilin FctB, revealing an immunoglobulin (Ig)-like N-terminal domain with an extended proline-rich tail. Unexpected structural homology between the FctB Ig-like domain and the N-terminal domain of the GAS shaft pilin helps explain the use of the same sortase for polymerization of the shaft and its attachment to FctB. It also enabled the identification, from mass spectral data, of the lysine residue involved in the covalent linkage of FctB to the shaft. The proline-rich tail forms a polyproline-II helix that appears to be a common feature of the basal (cell wall-anchoring) pilins. Together, our results indicate distinct structural elements in the pilin proteins that play a role in selecting for the appropriate sortases and thereby help orchestrate the ordered assembly of the pilus.
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Affiliation(s)
- Christian Linke
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Abstract
Streptococci are clinically important Gram-positive bacteria that are capable to cause a wide variety of diseases in humans and animals. Phylogenetic analyses based on 16S rRNA sequences of the streptococcal species reveal a clustering pattern, reflecting, with a few exceptions, their pathogenic potential and ecological preferences. Microbial adhesion to host tissues is the initial critical event in the pathogenesis of most infections. Streptococci use multiple adhesins to attach to the epithelium, and their expression is regulated in response to environmental and growth conditions. Bacterial adhesins recognize and bind cell surface molecules and extracellular matrix components through specific domains that for certain adhesin families have been well defined and found conserved across the streptococcal species. In this review, we present the different streptococcal adhesin families categorized on the basis of their adhesive properties and structural characteristics, and, when available, we focus the attention on conserved functional domains.
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Affiliation(s)
- Monica Moschioni
- Novartis Vaccines and Diagnostics, Via Fiorentina 1, Siena, Italy
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Budzik JM, Oh SY, Schneewind O. Sortase D forms the covalent bond that links BcpB to the tip of Bacillus cereus pili. J Biol Chem 2009; 284:12989-97. [PMID: 19269972 PMCID: PMC2676031 DOI: 10.1074/jbc.m900927200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 03/05/2009] [Indexed: 11/06/2022] Open
Abstract
Bacillus cereus and other Gram-positive bacteria elaborate pili via a sortase D-catalyzed transpeptidation mechanism from major and minor pilin precursor substrates. After cleavage of the LPXTG sorting signal of the major pilin, BcpA, sortase D forms an amide bond between the C-terminal threonine and the amino group of lysine within the YPKN motif of another BcpA subunit. Pilus assembly terminates upon sortase A cleavage of the BcpA sorting signal, resulting in a covalent bond between BcpA and the cell wall cross-bridge. Here, we show that the IPNTG sorting signal of BcpB, the minor pilin, is cleaved by sortase D but not by sortase A. The C-terminal threonine of BcpB is amide-linked to the YPKN motif of BcpA, thereby positioning BcpB at the tip of pili. Thus, unique attributes of the sorting signals of minor pilins provide Gram-positive bacteria with a universal mechanism ordering assembly of pili.
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Affiliation(s)
- Jonathan M Budzik
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
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Budzik JM, Oh SY, Schneewind O. Cell wall anchor structure of BcpA pili in Bacillus anthracis. J Biol Chem 2008; 283:36676-86. [PMID: 18940793 PMCID: PMC2605976 DOI: 10.1074/jbc.m806796200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Indexed: 11/06/2022] Open
Abstract
Assembly of pili in Gram-positive bacteria and their attachment to the cell wall envelope are mediated by sortases. In Bacillus cereus and its close relative Bacillus anthracis, the major pilin protein BcpA is cleaved between the threonine and the glycine of its C-terminal LPXTG motif sorting signal by the pilin-specific sortase D. The resulting acyl enzyme intermediate is relieved by the nucleophilic attack of the side-chain amino group of lysine within the YPKN motif of another BcpA subunit. Cell wall anchoring of assembled BcpA pili requires sortase A, which also cleaves the LPXTG sorting signal of BcpA between its threonine and glycine residues. We show here that sortases A and D require only the C-terminal sorting signal of BcpA for substrate cleavage. Unlike sortase D, which accepts the YPKN motif as a nucleophile, sortase A forms an amide bond between the BcpA C-terminal carboxyl group of threonine and the side-chain amino group of diaminopimelic acid within the cell wall peptidoglycan of bacilli. These results represent the first demonstration of a cell wall anchor structure for pili, which are deposited by sortase A into the envelope of many different microbes.
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Affiliation(s)
- Jonathan M Budzik
- Department of Microbiology, University of Chicago, Chicago, Illinois 60637, USA
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