Chaperone-tip adhesin complex is vital for synergistic activation of CFA/I fimbriae biogenesis

PLoS Pathog. 2020 Oct 2;16(10):e1008848. doi: 10.1371/journal.ppat.1008848. eCollection 2020 Oct.

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.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adhesins, Bacterial / metabolism*
  • Amino Acid Sequence
  • Cytoplasm
  • Enterotoxigenic Escherichia coli / physiology*
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Fimbriae Proteins / genetics
  • Fimbriae Proteins / metabolism*
  • Fimbriae, Bacterial / physiology*
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism*
  • Protein Conformation
  • Sequence Homology, Amino Acid

Substances

  • Adhesins, Bacterial
  • Escherichia coli Proteins
  • Molecular Chaperones
  • Fimbriae Proteins

Grants and funding

This work was supported in part by the National Key Research and Development Plan (Grant 2016YFA0502700), by National Natural Science Foundation of China (Grant No. 81501787, 81670008 and 81871615), by Ministry of Science and Technology of the People's Republic of China (No.2018ZX09201018-005), and National Mega-project for Innovative Drugs (2019ZX09721001-001-001). It is partially supported by the United States Army Infectious Disease Research Program Work Unit A1207 and the Henry M. Jackson Foundation for the Advancement of Military Medicine (to M.G.P.). This research was also supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.