Suppressor Mutations in Type II Secretion Mutants of Vibrio cholerae: Inactivation of the VesC Protease

Chelsea S. Rule, Young Jun Park, Jaclyn R. Delarosa, Stewart Turley, Wim G.J. Hol, Sarah McColm, Colby Gura, Frank DiMaio, Konstantin V. Korotkov, Maria Sandkvist

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The type II secretion system (T2SS) is a conserved transport pathway responsible for the secretion of a range of virulence factors by many pathogens, including Vibrio cholerae. Disruption of the T2SS genes in V. cholerae results in loss of secretion, changes in cell envelope function, and growth defects. While T2SS mutants are viable, high-throughput genomic analyses have listed these genes among essential genes. To investigate whether secondary mutations arise as a consequence of T2SS inactivation, e sequenced the genomes of six V. cholerae T2SS mutants with deletions or insertions in either the epsG, epsL, or epsM genes and identified secondary mutations in all mutants. Two of the six T2SS mutants contain distinct mutations in the gene encoding the T2SS-secreted protease VesC. Other mutations were found in genes coding for V.cholerae cell envelope proteins. Subsequent sequence analysis of the vesC gene in 92 additional T2SS mutant isolates identified another 19 unique mutations including insertions or deletions, sequence duplications, and single-nucleotide changes resulting in amino acid substitutions in the VesC protein. Analysis of VesC variants and the X-ray crystallographic structure of wild-type VesC suggested that all mutations lead to loss of VesC production and/or function. One possible mechanism by which V. cholerae T2SS mutagenesis can be tolerated is through selection of vesC-inactivating mutations, which may, in part, suppress cell envelope damage, establishing permissive conditions for the disruption of the T2SS.

Original languageEnglish
Pages (from-to)1-18
Number of pages18
Issue number6
StatePublished - 2020

Bibliographical note

Funding Information:
This study was supported by the National Institute of Allergy and Infectious Diseases grants R01AI049294 and R01AI137085 (to M.S.) and R01AI034501 (to W.G.J.H.). Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research and by the National Institutes of Health, National Institute of General Medical Sciences (including P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health. We declare that we have no conflicts of interest with the contents of this article.

Publisher Copyright:
© 2020 Rule et al. This is an openaccess article distributed under the terms of the Creative Commons Attribution 4.0 International license.


  • Vibrio cholerae
  • protein structure
  • serine protease
  • suppressor
  • type II secretion system

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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