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Nash ZM, Inatsuka CS, Cotter PA, Johnson RM. Bordetella filamentous hemagglutinin and adenylate cyclase toxin interactions on the bacterial surface are consistent with FhaB-mediated delivery of ACT to phagocytic cells. mBio 2024; 15:e0063224. [PMID: 38534159 PMCID: PMC11077949 DOI: 10.1128/mbio.00632-24] [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: 03/01/2024] [Accepted: 03/07/2024] [Indexed: 03/28/2024] Open
Abstract
Bordetella species that cause respiratory infections in mammals include B. pertussis, which causes human whooping cough, and B. bronchiseptica, which infects nearly all mammals. Both bacterial species produce filamentous hemagglutinin (FhaB) and adenylate cyclase toxin (ACT), prominent surface-associated and secreted virulence factors that contribute to persistence in the lower respiratory tract by inhibiting clearance by phagocytic cells. FhaB and ACT proteins interact with themselves, each other, and host cells. Using immunoblot analyses, we showed that ACT binds to FhaB on the bacterial surface before it can be detected in culture supernatants. We determined that SphB1, a surface protease identified based on its requirement for FhaB cleavage, is also required for ACT cleavage, and we determined that the presence of ACT blocks SphB1-dependent and -independent cleavage of FhaB, but the presence of FhaB does not affect SphB1-dependent cleavage of ACT. The primary SphB1-dependent cleavage site on ACT is proximal to ACT's active site, in a region that is critical for ACT activity. We also determined that FhaB-bound ACT on the bacterial surface can intoxicate host cells producing CR3, the receptor for ACT. In addition to increasing our understanding of FhaB, ACT, and FhaB-ACT interactions on the Bordetella surface, our data are consistent with a model in which FhaB functions as a novel toxin delivery system by binding to ACT and allowing its release upon binding of ACT to its receptor, CR3, on phagocytic cells.IMPORTANCEBacteria need to control the variety, abundance, and conformation of proteins on their surface to survive. Members of the Gram-negative bacterial genus Bordetella include B. pertussis, which causes whooping cough in humans, and B. bronchiseptica, which causes respiratory infections in a broad range of mammals. These species produce two prominent virulence factors, the two-partner secretion (TPS) effector FhaB and adenylate cyclase toxin (ACT), that interact with themselves, each other, and host cells. Here, we determined that ACT binds FhaB on the bacterial surface before being detected in culture supernatants and that ACT bound to FhaB can be delivered to eukaryotic cells. Our data are consistent with a model in which FhaB delivers ACT specifically to phagocytic cells. This is the first report of a TPS system facilitating the delivery of a separate polypeptide toxin to target cells and expands our understanding of how TPS systems contribute to bacterial pathogenesis.
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Affiliation(s)
- Zachary M. Nash
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Carol S. Inatsuka
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Peggy A. Cotter
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Richard M. Johnson
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
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Harkness RW, Zhao H, Toyama Y, Schuck P, Kay LE. Exploring Host-Guest Interactions within a 600 kDa DegP Protease Cage Complex Using Hydrodynamics Measurements and Methyl-TROSY NMR. J Am Chem Soc 2024; 146:8242-8259. [PMID: 38477967 DOI: 10.1021/jacs.3c13247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
The DegP protease-chaperone operates within the periplasm of Gram-negative bacteria, where it assists in the regulation of protein homeostasis, promotes virulence, and is essential to survival under stress. To carry out these tasks, DegP forms a network of preorganized apo oligomers that facilitate the capture of substrates within distributions of cage-like complexes which expand to encapsulate clients of various sizes. Although the architectures of DegP cage complexes are well understood, little is known about the structures, dynamics, and interactions of client proteins within DegP cages and the relationship between client structural dynamics and function. Here, we probe host-guest interactions within a 600 kDa DegP cage complex throughout the DegP activation cycle using a model α-helical client protein through a combination of hydrodynamics measurements, methyl-transverse relaxation optimized spectroscopy-based solution nuclear magnetic resonance studies, and proteolytic activity assays. We find that in the presence of the client, DegP cages assemble cooperatively with few intermediates. Our data further show that the N-terminal half of the bound client, which projects into the interior of the cages, is predominantly unfolded and flexible, and exchanges between multiple conformational states over a wide range of time scales. Finally, we show that a concerted structural transition of the protease domains of DegP occurs upon client engagement, leading to activation. Together, our findings support a model of DegP as a highly cooperative and dynamic molecular machine that stabilizes unfolded states of clients, primarily via interactions with their C-termini, giving rise to efficient cleavage.
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Affiliation(s)
- Robert W Harkness
- Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto M5S 1A8, Canada
- Department of Chemistry, University of Toronto, Toronto M5S 3H6, Canada
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto M5G 0A4, Canada
| | - Huaying Zhao
- Laboratory of Dynamics of Macromolecular Assembly, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Yuki Toyama
- Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto M5S 1A8, Canada
- Department of Chemistry, University of Toronto, Toronto M5S 3H6, Canada
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto M5G 0A4, Canada
| | - Peter Schuck
- Laboratory of Dynamics of Macromolecular Assembly, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Lewis E Kay
- Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto M5S 1A8, Canada
- Department of Chemistry, University of Toronto, Toronto M5S 3H6, Canada
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto M5G 0A4, Canada
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Luo H, Qu X, Deng X, He L, Wu Y, Liu Y, He D, Yin J, Wang B, Gan F, Tang B, Tang XF. HtrAs are essential for the survival of the haloarchaeon Natrinema gari J7-2 in response to heat, high salinity, and toxic substances. Appl Environ Microbiol 2024; 90:e0204823. [PMID: 38289131 PMCID: PMC10880668 DOI: 10.1128/aem.02048-23] [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: 11/13/2023] [Accepted: 12/24/2023] [Indexed: 02/22/2024] Open
Abstract
Bacterial and eukaryotic HtrAs can act as an extracytoplasmic protein quality control (PQC) system to help cells survive in stress conditions, but the functions of archaeal HtrAs remain unknown. Particularly, haloarchaea route most secretory proteins to the Tat pathway, enabling them to fold properly in well-controlled cytoplasm with cytosolic PQC systems before secretion. It is unclear whether HtrAs are required for haloarchaeal survival and stress response. The haloarchaeon Natrinema gari J7-2 encodes three Tat signal peptide-bearing HtrAs (NgHtrA, NgHtrB, and NgHtrC), and the signal peptides of NgHtrA and NgHtrC contain a lipobox. Here, the in vitro analysis reveals that the three HtrAs show different profiles of temperature-, salinity-, and metal ion-dependent proteolytic activities and could exhibit chaperone-like activities to prevent the aggregation of reduced lysozyme when their proteolytic activities are inhibited at low temperatures or the active site is disrupted. The gene deletion and complementation assays reveal that NgHtrA and NgHtrC are essential for the survival of strain J7-2 at elevated temperature and/or high salinity and contribute to the resistance of this haloarchaeon to zinc and inhibitory substances generated from tryptone. Mutational analysis shows that the lipobox mediates membrane anchoring of NgHtrA or NgHtrC, and both the membrane-anchored and free extracellular forms of the two enzymes are involved in the stress resistance of strain J7-2, depending on the stress conditions. Deletion of the gene encoding NgHtrB in strain J7-2 causes no obvious growth defect, but NgHtrB can functionally substitute for NgHtrA or NgHtrC under some conditions.IMPORTANCEHtrA-mediated protein quality control plays an important role in the removal of aberrant proteins in the extracytoplasmic space of living cells, and the action mechanisms of HtrAs have been extensively studied in bacteria and eukaryotes; however, information about the function of archaeal HtrAs is scarce. Our results demonstrate that three HtrAs of the haloarchaeon Natrinema gari J7-2 possess both proteolytic and chaperone-like activities, confirming that the bifunctional nature of HtrAs is conserved across all three domains of life. Moreover, we found that NgHtrA and NgHtrC are essential for the survival of strain J7-2 under stress conditions, while NgHtrB can serve as a substitute for the other two HtrAs under certain circumstances. This study provides the first biochemical and genetic evidence of the importance of HtrAs for the survival of haloarchaea in response to stresses.
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Affiliation(s)
- Hongyi Luo
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiaoyi Qu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xi Deng
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Liping He
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yi Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yang Liu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Dan He
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jing Yin
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Bingxue Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Fei Gan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation, Ministry of Education and Hubei Province, Wuhan, China
| | - Bing Tang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation, Ministry of Education and Hubei Province, Wuhan, China
| | - Xiao-Feng Tang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation, Ministry of Education and Hubei Province, Wuhan, China
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Golshani M, Rahman WU, Osickova A, Holubova J, Lora J, Balashova N, Sebo P, Osicka R. Filamentous Hemagglutinin of Bordetella pertussis Does Not Interact with the β 2 Integrin CD11b/CD18. Int J Mol Sci 2022; 23:12598. [PMID: 36293453 PMCID: PMC9604300 DOI: 10.3390/ijms232012598] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 01/04/2024] Open
Abstract
The pertussis agent Bordetella pertussis produces a number of virulence factors, of which the filamentous hemagglutinin (FhaB) plays a role in B. pertussis adhesion to epithelial and phagocytic cells. Moreover, FhaB was recently found to play a crucial role in nasal cavity infection and B. pertussis transmission to new hosts. The 367 kDa FhaB protein translocates through an FhaC pore to the outer bacterial surface and is eventually processed to a ~220 kDa N-terminal FHA fragment by the SphB1 protease. A fraction of the mature FHA then remains associated with bacterial cell surface, while most of FHA is shed into the bacterial environment. Previously reported indirect evidence suggested that FHA, or its precursor FhaB, may bind the β2 integrin CD11b/CD18 of human macrophages. Therefore, we assessed FHA binding to various cells producing or lacking the integrin and show that purified mature FHA does not bind CD11b/CD18. Further results then revealed that the adhesion of B. pertussis to cells does not involve an interaction between the bacterial surface-associated FhaB and/or mature FHA and the β2 integrin CD11b/CD18. In contrast, FHA binding was strongly inhibited at micromolar concentrations of heparin, corroborating that the cell binding of FHA is ruled by the interaction of its heparin-binding domain with sulfated glycosaminoglycans on the cell surface.
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Affiliation(s)
- Maryam Golshani
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Waheed Ur Rahman
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Adriana Osickova
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jana Holubova
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jinery Lora
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St., Philadelphia, PA 19104, USA
| | - Nataliya Balashova
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St., Philadelphia, PA 19104, USA
| | - Peter Sebo
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Radim Osicka
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
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Job V, Gomez-Valero L, Renier A, Rusniok C, Bouillot S, Chenal-Francisque V, Gueguen E, Adrait A, Robert-Genthon M, Jeannot K, Panchev P, Elsen S, Fauvarque MO, Couté Y, Buchrieser C, Attrée I. Genomic erosion and horizontal gene transfer shape functional differences of the ExlA toxin in Pseudomonas spp. iScience 2022; 25:104596. [PMID: 35789842 PMCID: PMC9250014 DOI: 10.1016/j.isci.2022.104596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 03/15/2022] [Accepted: 06/08/2022] [Indexed: 12/31/2022] Open
Abstract
Two-partner secretion (TPS) is widespread in the bacterial world. The pore-forming TPS toxin ExlA of Pseudomonas aeruginosa is conserved in pathogenic and environmental Pseudomonas. While P. chlororaphis and P. entomophila displayed ExlA-dependent killing, P. putida did not cause damage to eukaryotic cells. ExlA proteins interacted with epithelial cell membranes; however, only ExlAPch induced the cleavage of the adhesive molecule E-cadherin. ExlA proteins participated in insecticidal activity toward the larvae of Galleria mellonella and the fly Drosophila melanogaster. Evolutionary analyses demonstrated that the differences in the C-terminal domains are partly due to horizontal movements of the operon within the genus Pseudomonas. Reconstruction of the evolutionary history revealed the complex horizontal acquisitions. Together, our results provide evidence that conserved TPS toxins in environmental Pseudomonas play a role in bacteria-insect interactions and discrete differences in CTDs may determine their specificity and mode of action toward eukaryotic cells. ExlA is a two-partner secreted toxin conserved across Pseudomonas spp. Environmental Pseudomonas strains encode ExlA with different cytotoxic activities ExlA of environmental Pseudomonas strains play a role in bacteria-insect interactions ExlBA operon shows a complex evolutionary history of horizontal gene transfer
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Affiliation(s)
- Viviana Job
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Laura Gomez-Valero
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Adèle Renier
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Christophe Rusniok
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Stephanie Bouillot
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Viviane Chenal-Francisque
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Erwan Gueguen
- University of Lyon, Université Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et Pathogénie, Lyon, France
| | - Annie Adrait
- Université Grenoble Alpes, INSERM, CEA, UMR BioSanté U1292, Grenoble, France
| | - Mylène Robert-Genthon
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Katy Jeannot
- Centre National de Référence de la Résistance aux Antibiotiques, Laboratoire de Bactériologie, Centre Hospitalier Universitaire Jean Minjoz, UMR6249 CNRS, Université de Bourgogne-Franche Comté, Besançon, France
| | - Peter Panchev
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Sylvie Elsen
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | | | - Yohann Couté
- Université Grenoble Alpes, INSERM, CEA, UMR BioSanté U1292, Grenoble, France
- CNRS, CEA, FR2048, Grenoble, France
| | - Carmen Buchrieser
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
- Corresponding author
| | - Ina Attrée
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
- Corresponding author
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Gutierrez MDLP, Wong TY, Damron FH, Fernández J, Sisti F. Cyclic di-GMP Regulates the Type III Secretion System and Virulence in Bordetella bronchiseptica. Infect Immun 2022; 90:e0010722. [PMID: 35612302 PMCID: PMC9202433 DOI: 10.1128/iai.00107-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 03/28/2022] [Indexed: 01/14/2023] Open
Abstract
The second messenger cyclic di-GMP (c-di-GMP) is a ubiquitous molecule in bacteria that regulates diverse phenotypes. Among them, motility and biofilm formation are the most studied. Furthermore, c-di-GMP has been suggested to regulate virulence factors, making it important for pathogenesis. Previously, we reported that c-di-GMP regulates biofilm formation and swimming motility in Bordetella bronchiseptica. Here, we present a multi-omics approach for the study of B. bronchiseptica strains expressing different cytoplasmic c-di-GMP levels, including transcriptome sequencing (RNA-seq) and shotgun proteomics with label-free quantification. We detected 64 proteins significantly up- or downregulated in either low or high c-di-GMP levels and 358 genes differentially expressed between strains with high c-di-GMP levels and the wild-type strain. Among them, we found genes for stress-related proteins, genes for nitrogen metabolism enzymes, phage-related genes, and virulence factor genes. Interestingly, we observed that a virulence factor like the type III secretion system (TTSS) was regulated by c-di-GMP. B. bronchiseptica with high c-di-GMP levels showed significantly lower levels of TTSS components like Bsp22, BopN, and Bcr4. These findings were confirmed by independent methods, such as quantitative reverse transcription-PCR (q-RT-PCR) and Western blotting. Higher intracellular levels of c-di-GMP correlated with an impaired capacity to induce cytotoxicity in a eukaryotic cell in vitro and with attenuated virulence in a murine model. This work presents data that support the role that the second messenger c-di-GMP plays in the pathogenesis of Bordetella.
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Affiliation(s)
- María de la Paz Gutierrez
- Instituto de Biotecnología y Biología Molecular-CCT-CONICET-La Plata, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Ting Y. Wong
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University School of Medicine, Morgantown, West Virginia, USA
- Vaccine Development Center at West Virginia University Health Sciences Center, Morgantown, West Virginia, USA
| | - Fredrick Heath Damron
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University School of Medicine, Morgantown, West Virginia, USA
- Vaccine Development Center at West Virginia University Health Sciences Center, Morgantown, West Virginia, USA
| | - Julieta Fernández
- Instituto de Biotecnología y Biología Molecular-CCT-CONICET-La Plata, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Federico Sisti
- Instituto de Biotecnología y Biología Molecular-CCT-CONICET-La Plata, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
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Bacterial Carboxyl-Terminal Processing Proteases Play Critical Roles in the Cell Envelope and Beyond. J Bacteriol 2022; 204:e0062821. [PMID: 35293777 PMCID: PMC9017358 DOI: 10.1128/jb.00628-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Proteolysis is essential throughout life, and as more proteases are characterized, our understanding of the roles they play continues to expand. Among other things, proteases are critical for protein turnover and quality control, the activation or inactivation of some enzymes, and they are integral components of signal transduction pathways. This review focuses on a family of proteases in bacteria known as the carboxyl-terminal processing proteases, or CTPs. Members of this family occur in all domains of life. In bacteria, CTPs have emerged as important enzymes that have been implicated in critical processes including regulation, stress response, peptidoglycan remodeling, and virulence. Here, we provide an overview of the roles that CTPs play in diverse bacterial species, and some of the underlying mechanisms. We also describe the structures of some bacterial CTPs, and their adaptor proteins, which have revealed striking differences in arrangements and mechanisms of action. Finally, we discuss what little is known about the distinguishing features of CTP substrates and cleavage sites, and speculate about how CTP activities might be regulated in the bacterial cell. Compared with many other proteases, the study of bacterial CTPs is still in its infancy, but it has now become clear that they affect fundamental processes in many different species. This is a protease family with broad significance, and one that holds the promise of more high impact discoveries to come.
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