A critical region in the FlaA flagellin facilitates filament formation of the Vibrio cholerae flagellum

Mylea A. Echazarreta, Johnathan L. Kepple, Li Hua Yen, Yue Chen, Karl E. Klose

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Vibrio cholerae is a Gram-negative bacterium with a monotrichous flagellum that causes the human disease cholera. Flagellum-mediated motility is an integral part of the bacterial life cycle inside the host and in the aquatic environment. The V. cholerae flagellar filament is composed of five flagellin subunits (FlaA, FlaB, FlaC, FlaD, and FlaE); however, only FlaA is necessary and sufficient for filament synthesis. flaA is transcribed from a class III flagellar promoter, whereas the other four flagellins are transcribed from class IV promoters. However, expressing flaA from a class IV promoter still facilitated motility in a strain that was otherwise lacking all five flagellins (ΔflaA-E). Furthermore, FlaA from V. parahaemolyticus (FlaAVP; 77% identity) supported motility of the V. cholerae ΔflaA-E strain, whereas FlaA from V. vulnificus (FlaAVV; 75% identity) did not, indicating that FlaA amino acid sequence is responsible for its critical role in flagellar synthesis. Chimeric proteins composed of different domains of FlaAVC and FlaD or FlaAVV revealed that the N-terminal D1 domain (D1N) contains an important region required for FlaA function. Further analyses of chimeric FlaAVC-FlaD proteins identified a lysine residue present at position 145 of the other flagellins but absent from FlaAVC that can prevent monofilament formation. Moreover, the D1N region of amino acids 87 to 153 of FlaAVV inserted into FlaAVC allows monofilament formation but not motility, apparently due to the lack of filament curvature. These results identify residues within the D1N domain that allow FlaAVC to fold into a functional filament structure and suggest that FlaAVC assists correct folding of the other flagellins.

Original languageEnglish (US)
Article numbere00029-18
JournalJournal of bacteriology
Volume200
Issue number15
DOIs
StatePublished - Aug 1 2018
Externally publishedYes

Keywords

  • Cholera
  • Filament
  • Flagella
  • Flagellar motility
  • Swimming

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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