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He LH, Wang H, Liu Y, Kang M, Li T, Li CC, Tong AP, Zhu YB, Song YJ, Savarino SJ, Prouty MG, Xia D, Bao R. Chaperone-tip adhesin complex is vital for synergistic activation of CFA/I fimbriae biogenesis. PLoS Pathog 2020; 16:e1008848. [PMID: 33007034 PMCID: PMC7531860 DOI: 10.1371/journal.ppat.1008848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 07/30/2020] [Indexed: 02/05/2023] Open
Abstract
Colonization factor CFA/I defines the major adhesive fimbriae of enterotoxigenic Escherichia coli and mediates bacterial attachment to host intestinal epithelial cells. The CFA/I fimbria consists of a tip-localized minor adhesive subunit, CfaE, and thousands of copies of the major subunit CfaB polymerized into an ordered helical rod. Biosynthesis of CFA/I fimbriae requires the assistance of the periplasmic chaperone CfaA and outer membrane usher CfaC. Although the CfaE subunit is proposed to initiate the assembly of CFA/I fimbriae, how it performs this function remains elusive. Here, we report the establishment of an in vitro assay for CFA/I fimbria assembly and show that stabilized CfaA-CfaB and CfaA-CfaE binary complexes together with CfaC are sufficient to drive fimbria formation. The presence of both CfaA-CfaE and CfaC accelerates fimbria formation, while the absence of either component leads to linearized CfaB polymers in vitro. We further report the crystal structure of the stabilized CfaA-CfaE complex, revealing features unique for biogenesis of Class 5 fimbriae.
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Affiliation(s)
- Li-hui He
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Hao Wang
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States of America
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Yang Liu
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States of America
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Mei Kang
- Department of Laboratory medicine, West China Hospital, Sichuan University, Chengdu, China
| | - Tao Li
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Chang-cheng Li
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Ai-ping Tong
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yi-bo Zhu
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Ying-jie Song
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Stephen J. Savarino
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, United States of America
- Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, MD, United States of America
| | - Michael G. Prouty
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, United States of America
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Rui Bao
- Center of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
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Classical chaperone-usher (CU) adhesive fimbriome: uropathogenic Escherichia coli (UPEC) and urinary tract infections (UTIs). Folia Microbiol (Praha) 2019; 65:45-65. [DOI: 10.1007/s12223-019-00719-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 05/20/2019] [Indexed: 12/17/2022]
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Pakharukova N, McKenna S, Tuittila M, Paavilainen S, Malmi H, Xu Y, Parilova O, Matthews S, Zavialov AV. Archaic and alternative chaperones preserve pilin folding energy by providing incomplete structural information. J Biol Chem 2018; 293:17070-17080. [PMID: 30228191 DOI: 10.1074/jbc.ra118.004170] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/14/2018] [Indexed: 11/06/2022] Open
Abstract
Adhesive pili are external component of fibrous adhesive organelles and help bacteria attach to biotic or abiotic surfaces. The biogenesis of adhesive pili via the chaperone-usher pathway (CUP) is independent of external energy sources. In the classical CUP, chaperones transport assembly-competent pilins in a folded but expanded conformation. During donor-strand exchange, pilins subsequently collapse, producing a tightly packed hydrophobic core and releasing the necessary free energy to drive fiber formation. Here, we show that pilus biogenesis in non-classical, archaic, and alternative CUPs uses a different source of conformational energy. High-resolution structures of the archaic Csu-pili system from Acinetobacter baumannii revealed that non-classical chaperones employ a short donor strand motif that is insufficient to fully complement the pilin fold. This results in chaperone-bound pilins being trapped in a substantially unfolded intermediate. The exchange of this short motif with the longer donor strand from adjacent pilin provides the full steric information essential for folding, and thereby induces a large unfolded-to-folded conformational transition to drive assembly. Our findings may inform the development of anti-adhesion drugs (pilicides) to combat bacterial infections.
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Affiliation(s)
- Natalia Pakharukova
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
| | - Sophie McKenna
- the Department of Life Sciences, Imperial College London, South Kensington Campus, London SW72AZ, United Kingdom
| | - Minna Tuittila
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
| | - Sari Paavilainen
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
| | - Henri Malmi
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
| | - Yingqi Xu
- the Department of Life Sciences, Imperial College London, South Kensington Campus, London SW72AZ, United Kingdom
| | - Olena Parilova
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
| | - Steve Matthews
- the Department of Life Sciences, Imperial College London, South Kensington Campus, London SW72AZ, United Kingdom
| | - Anton V Zavialov
- From the Department of Chemistry, University of Turku, Joint Biotechnology Laboratory (JBL), Arcanum, Vatselankatu 2, Turku FIN-20500, Finland and
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Bao R, Liu Y, Savarino SJ, Xia D. Off-pathway assembly of fimbria subunits is prevented by chaperone CfaA of CFA/I fimbriae from enterotoxigenic E. coli. Mol Microbiol 2016; 102:975-991. [PMID: 27627030 DOI: 10.1111/mmi.13530] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/10/2016] [Accepted: 09/12/2016] [Indexed: 11/29/2022]
Abstract
The assembly of the class 5 colonization factor antigen I (CFA/I) fimbriae of enterotoxigenic E. coli was proposed to proceed via the alternate chaperone-usher pathway. Here, we show that in the absence of the chaperone CfaA, CfaB, the major pilin subunit of CFA/I fimbriae, is able to spontaneously refold and polymerize into cyclic trimers. CfaA kinetically traps CfaB to form a metastable complex that can be stabilized by mutations. Crystal structure of the stabilized complex reveals distinctive interactions provided by CfaA to trap CfaB in an assembly competent state through donor-strand complementation (DSC) and cleft-mediated anchorage. Mutagenesis indicated that DSC controls the stability of the chaperone-subunit complex and the cleft-mediated anchorage of the subunit C-terminus additionally assist in subunit refolding. Surprisingly, over-stabilization of the chaperone-subunit complex led to delayed fimbria assembly, whereas destabilizing the complex resulted in no fimbriation. Thus, CfaA acts predominantly as a kinetic trap by stabilizing subunit to avoid its off-pathway self-polymerization that results in energetically favorable trimers and could serve as a driving force for CFA/I pilus assembly, representing an energetic landscape unique to class 5 fimbria assembly.
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Affiliation(s)
- Rui Bao
- Division of Infectious Diseases, National Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy, West China Hospitals, Sichuan University, Chengdu, 610041, China.,Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892, USA
| | - Yang Liu
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, 20910-7500, USA
| | - Stephen J Savarino
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD, 20910-7500, USA.,Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814-4799, USA
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, 20892, USA
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Binding of CFA/I Pili of Enterotoxigenic Escherichia coli to Asialo-GM1 Is Mediated by the Minor Pilin CfaE. Infect Immun 2016; 84:1642-1649. [PMID: 26975993 DOI: 10.1128/iai.01562-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/06/2016] [Indexed: 11/20/2022] Open
Abstract
CFA/I pili are representatives of a large family of related pili that mediate the adherence of enterotoxigenic Escherichia coli to intestinal epithelial cells. They are assembled via the alternate chaperone-usher pathway and consist of two subunits, CfaB, which makes up the pilus shaft and a single pilus tip-associated subunit, CfaE. The current model of pilus-mediated adherence proposes that CFA/I has two distinct binding activities; the CfaE subunit is responsible for binding to receptors of unknown structure on erythrocyte and intestinal epithelial cell surfaces, while CfaB binds to various glycosphingolipids, including asialo-GM1. In this report, we present two independent lines of evidence that, contrary to the existing model, CfaB does not bind to asialo-GM1 independently of CfaE. Neither purified CfaB subunits nor CfaB assembled into pili bind to asialo-GM1. Instead, we demonstrate that binding activity toward asialo-GM1 resides in CfaE and this is essential for pilus binding to Caco-2 intestinal epithelial cells. We conclude that the binding activities of CFA/I pili for asialo-GM1, erythrocytes, and intestinal cells are inseparable, require the same amino acid residues in CfaE, and therefore depend on the same or very similar binding mechanisms.
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Pakharukova N, Garnett JA, Tuittila M, Paavilainen S, Diallo M, Xu Y, Matthews SJ, Zavialov AV. Structural Insight into Archaic and Alternative Chaperone-Usher Pathways Reveals a Novel Mechanism of Pilus Biogenesis. PLoS Pathog 2015; 11:e1005269. [PMID: 26587649 PMCID: PMC4654587 DOI: 10.1371/journal.ppat.1005269] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/22/2015] [Indexed: 11/18/2022] Open
Abstract
Gram-negative pathogens express fibrous adhesive organelles that mediate targeting to sites of infection. The major class of these organelles is assembled via the classical, alternative and archaic chaperone-usher pathways. Although non-classical systems share a wider phylogenetic distribution and are associated with a range of diseases, little is known about their assembly mechanisms. Here we report atomic-resolution insight into the structure and biogenesis of Acinetobacter baumannii Csu and Escherichia coli ECP biofilm-mediating pili. We show that the two non-classical systems are structurally related, but their assembly mechanism is strikingly different from the classical assembly pathway. Non-classical chaperones, unlike their classical counterparts, maintain subunits in a substantially disordered conformational state, akin to a molten globule. This is achieved by a unique binding mechanism involving the register-shifted donor strand complementation and a different subunit carboxylate anchor. The subunit lacks the classical pre-folded initiation site for donor strand exchange, suggesting that recognition of its exposed hydrophobic core starts the assembly process and provides fresh inspiration for the design of inhibitors targeting chaperone-usher systems.
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Affiliation(s)
- Natalia Pakharukova
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - James A. Garnett
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Minna Tuittila
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - Sari Paavilainen
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - Mamou Diallo
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Yingqi Xu
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Steve J. Matthews
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Anton V. Zavialov
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
- * E-mail:
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Garnett JA, Diallo M, Matthews SJ. Purification, crystallization and preliminary X-ray diffraction analysis of the Escherichia coli common pilus chaperone EcpB. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2015; 71:676-9. [PMID: 26057794 PMCID: PMC4461329 DOI: 10.1107/s2053230x15006354] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 03/28/2015] [Indexed: 11/22/2022]
Abstract
In Escherichia coli, the common pilus (Ecp) belongs to an alternative chaperone–usher pathway that plays a major role in both early biofilm formation and host-cell adhesion. Initial attempts at crystallizing the chaperone EcpB using natively purified protein from the bacterial periplasm were not successful; however, after the isolation of EcpB under denaturing conditions and subsequent refolding, crystals were obtained at pH 8.0 using the sitting-drop method of vapour diffusion. This is the first time that this refolding strategy has been used to purify CU chaperones. Pili are key cell-surface components that allow the attachment of bacteria to both biological and abiotic solid surfaces, whilst also mediating interactions between themselves. In Escherichia coli, the common pilus (Ecp) belongs to an alternative chaperone–usher (CU) pathway that plays a major role in both early biofilm formation and host-cell adhesion. The chaperone EcpB is involved in the biogenesis of the filament, which is composed of EcpA and EcpD. Initial attempts at crystallizing EcpB using natively purified protein from the bacterial periplasm were not successful; however, after the isolation of EcpB under denaturing conditions and subsequent refolding, crystals were obtained at pH 8.0 using the sitting-drop method of vapour diffusion. Diffraction data have been processed to 2.4 Å resolution. These crystals belonged to the trigonal space group P3121 or P3221, with unit-cell parameters a = b = 62.65, c = 121.14 Å and one monomer in the asymmetric unit. Molecular replacement was unsuccessful, but selenomethionine-substituted protein and heavy-atom derivatives are being prepared for phasing. The three-dimensional structure of EcpB will provide invaluable information on the subtle mechanistic differences in biogenesis between the alternative and classical CU pathways. Furthermore, this is the first time that this refolding strategy has been used to purify CU chaperones, and it could be implemented in similar systems where it has not been possible to obtain highly ordered crystals.
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Affiliation(s)
- James A Garnett
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, England
| | - Mamou Diallo
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, England
| | - Steve J Matthews
- Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, England
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Mortezaei N, Epler CR, Shao PP, Shirdel M, Singh B, McVeigh A, Uhlin BE, Savarino SJ, Andersson M, Bullitt E. Structure and function of enterotoxigenic Escherichia coli fimbriae from differing assembly pathways. Mol Microbiol 2014; 95:116-26. [PMID: 25355550 DOI: 10.1111/mmi.12847] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/28/2014] [Indexed: 12/19/2022]
Abstract
Pathogenic enterotoxigenic Escherichia coli (ETEC) are the major bacterial cause of diarrhea in young children in developing countries and in travelers, causing significant mortality in children. Adhesive fimbriae are a prime virulence factor for ETEC, initiating colonization of the small intestinal epithelium. Similar to other Gram-negative bacteria, ETEC express one or more diverse fimbriae, some assembled by the chaperone-usher pathway and others by the alternate chaperone pathway. Here, we elucidate structural and biophysical aspects and adaptations of each fimbrial type to its respective host niche. CS20 fimbriae are compared with colonization factor antigen I (CFA/I) fimbriae, which are two ETEC fimbriae assembled via different pathways, and with P-fimbriae from uropathogenic E. coli. Many fimbriae unwind from their native helical filament to an extended linear conformation under force, thereby sustaining adhesion by reducing load at the point of contact between the bacterium and the target cell. CFA/I fimbriae require the least force to unwind, followed by CS20 fimbriae and then P-fimbriae, which require the highest unwinding force. We conclude from our electron microscopy reconstructions, modeling and force spectroscopy data that the target niche plays a central role in the biophysical properties of fimbriae that are critical for bacterial pathophysiology.
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