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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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Tyagi S, Yadav RK, Krishnan V. Determination of the Crystal Structure of the Cell Wall-Anchored Proteins and Pilins. Methods Mol Biol 2024; 2727:159-191. [PMID: 37815717 DOI: 10.1007/978-1-0716-3491-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
Surface proteins and pili (or pilus) anchored on the Gram-positive bacterial cell wall play a vital role in adhesion, colonization, biofilm formation, and immunomodulation. The pilus consists of building blocks called pilins or pilus subunits. The surface proteins and pilins share some common sequences and structural features. They contain an N-terminal signal sequence and the C-terminal cell wall sorting region, enabling their transportation across the membrane and covalent attachment to the bacterial cell wall, respectively. The transpeptidase enzymes called sortases facilitate the covalent links between the pilins during the pilus assembly and between surface proteins or basal subunits of pili and peptidoglycan-bridge during the cell wall anchoring. Thus, elucidating three-dimensional structures for the surface proteins and pilins at the atomic level is essential for understanding the mechanism of adhesion, pilus assembly, and host interaction. This chapter aims to provide a general protocol for crystal structure determination of surface proteins and pilins anchored on the Gram-positive bacterial cell wall and substrates for sortases. The protocol involves the production of recombinant protein, crystallization, and structure determination by X-ray crystallography technique.
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Affiliation(s)
- Shivangi Tyagi
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Rajnesh Kumari Yadav
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Vengadesan Krishnan
- Laboratory of Structural Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India.
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3
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Sue CK, Cheung NA, Mahoney BJ, McConnell SA, Scully JM, Fu JY, Chang C, Ton-That H, Loo JA, Clubb RT. The basal and major pilins in the Corynebacterium diphtheriae SpaA pilus adopt similar structures that competitively react with the pilin polymerase. Biopolymers 2024; 115:e23539. [PMID: 37227047 PMCID: PMC11164409 DOI: 10.1002/bip.23539] [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: 01/31/2023] [Revised: 04/12/2023] [Accepted: 04/24/2023] [Indexed: 05/26/2023]
Abstract
Many species of pathogenic gram-positive bacteria display covalently crosslinked protein polymers (called pili or fimbriae) that mediate microbial adhesion to host tissues. These structures are assembled by pilus-specific sortase enzymes that join the pilin components together via lysine-isopeptide bonds. The archetypal SpaA pilus from Corynebacterium diphtheriae is built by the Cd SrtA pilus-specific sortase, which crosslinks lysine residues within the SpaA and SpaB pilins to build the shaft and base of the pilus, respectively. Here, we show that Cd SrtA crosslinks SpaB to SpaA via a K139(SpaB)-T494(SpaA) lysine-isopeptide bond. Despite sharing only limited sequence homology, an NMR structure of SpaB reveals striking similarities with the N-terminal domain of SpaA (N SpaA) that is also crosslinked by Cd SrtA. In particular, both pilins contain similarly positioned reactive lysine residues and adjacent disordered AB loops that are predicted to be involved in the recently proposed "latch" mechanism of isopeptide bond formation. Competition experiments using an inactive SpaB variant and additional NMR studies suggest that SpaB terminates SpaA polymerization by outcompeting N SpaA for access to a shared thioester enzyme-substrate reaction intermediate.
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Affiliation(s)
- Christopher K. Sue
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
| | - Nicole A. Cheung
- UCLA-DOE Institute for Genomics and Proteomics
- Molecular Biology Institute
| | - Brendan J. Mahoney
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
| | - Scott A. McConnell
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
| | - Jack M. Scully
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
| | - Janine Y. Fu
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
| | - Chungyu Chang
- Molecular Biology Institute
- Division of Oral and Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, 611 Charles Young Drive East, Los Angeles, CA 90095
| | - Hung Ton-That
- Molecular Biology Institute
- Division of Oral and Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, 611 Charles Young Drive East, Los Angeles, CA 90095
| | - Joseph A. Loo
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
- Molecular Biology Institute
| | - Robert T. Clubb
- Department of Chemistry and Biochemistry
- UCLA-DOE Institute for Genomics and Proteomics
- Molecular Biology Institute
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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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Post SE, Brito IL. Structural insight into protein-protein interactions between intestinal microbiome and host. Curr Opin Struct Biol 2022; 74:102354. [PMID: 35390637 DOI: 10.1016/j.sbi.2022.102354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 01/27/2022] [Accepted: 02/06/2022] [Indexed: 11/03/2022]
Abstract
Protein-protein interactions between the microbiome and host organism play an important role in shaping host health. These host-modulating proteins have therapeutic potential in treating microbiome-linked disorders such as inflammatory bowel disease and obesity. Structural analysis of interacting proteins provides highly mechanistic insight into the domains driving these interactions and the resulting influence on host cell processes. Here, we briefly review recent publication of microbiome protein structures involved in host binding interactions, the effects of these interactions on host physiology, and the need for further study to increase the ability to detect proteins with therapeutic potential.
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Affiliation(s)
- Sarah E Post
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA. https://twitter.com/@sarahpost140
| | - Ilana L Brito
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
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Prajapati A, Palva A, von Ossowski I, Krishnan V. LrpCBA pilus proteins of gut-dwelling Ligilactobacillus ruminis: crystallization and X-ray diffraction analysis. Acta Crystallogr F Struct Biol Commun 2021; 77:238-245. [PMID: 34341189 PMCID: PMC8329715 DOI: 10.1107/s2053230x21007263] [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: 06/15/2021] [Accepted: 07/13/2021] [Indexed: 11/10/2022] Open
Abstract
Adhesion to host surfaces for bacterial survival and colonization involves a variety of molecular mechanisms. Ligilactobacillus ruminis, a strict anaerobe and gut autochthonous (indigenous) commensal, relies on sortase-dependent pili (LrpCBA) for adherence to the intestinal inner walls, thereby withstanding luminal content flow. Here, the LrpCBA pilus is a promiscuous binder to gut collagen, fibronectin and epithelial cells. Structurally, the LrpCBA pilus displays a representative hetero-oligomeric arrangement and consists of three types of pilin subunit, each with its own location and function, i.e. tip LrpC for adhesion, basal LrpB for anchoring and backbone LrpA for length. To provide further structural insights into the assembly, anchoring and functional mechanisms of sortase-dependent pili, each of the L. ruminis pilus proteins was produced recombinantly for crystallization and X-ray diffraction analysis. Crystals of LrpC, LrpB, LrpA and truncated LrpA generated by limited proteolysis were obtained and diffracted to resolutions of 3.0, 1.5, 2.2 and 1.4 Å, respectively. Anomalous data were also collected from crystals of selenomethionine-substituted LrpC and an iodide derivative of truncated LrpA. Successful strategies for protein production, crystallization and derivatization are reported.
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Affiliation(s)
- Amar Prajapati
- Laboratory of Structural Biology, 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 Biology, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad 121 001, India
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Exploiting pilus-mediated bacteria-host interactions for health benefits. Mol Aspects Med 2021; 81:100998. [PMID: 34294411 DOI: 10.1016/j.mam.2021.100998] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/30/2021] [Accepted: 07/16/2021] [Indexed: 02/06/2023]
Abstract
Surface pili (or fimbriae) are an important but conspicuous adaptation of several genera and species of Gram-negative and Gram-positive bacteria. These long and non-flagellar multi-subunit adhesins mediate the initial contact that a bacterium has with a host or environment, and thus have come to be regarded as a key colonization factor for virulence activity in pathogens or niche adaptation in commensals. Pili in pathogenic bacteria are well recognized for their roles in the adhesion to host cells, colonization of tissues, and establishment of infection. As an 'anti-adhesive' ploy, targeting pilus-mediated attachment for disruption has become a potentially effective alternative to using antibiotics. In this review, we give a description of the several structurally distinct bacterial pilus types thus far characterized, and as well offer details about the intricacy of their individual structure, assembly, and function. With a molecular understanding of pilus biogenesis and pilus-mediated host interactions also provided, we go on to describe some of the emerging new approaches and compounds that have been recently developed to prevent the adhesion, colonization, and infection of piliated bacterial pathogens.
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