PLoS Pathogens (Nov 2021)

Flagellin lysine methyltransferase FliB catalyzes a [4Fe-4S] mediated methyl transfer reaction.

  • Chu Wang,
  • Christian Nehls,
  • Dirk Baabe,
  • Olaf Burghaus,
  • Robert Hurwitz,
  • Thomas Gutsmann,
  • Martin Bröring,
  • Michael Kolbe

DOI
https://doi.org/10.1371/journal.ppat.1010052
Journal volume & issue
Vol. 17, no. 11
p. e1010052

Abstract

Read online

The methyltransferase FliB posttranslationally modifies surface-exposed ɛ-N-lysine residues of flagellin, the protomer of the flagellar filament in Salmonella enterica (S. enterica). Flagellin methylation, reported originally in 1959, was recently shown to enhance host cell adhesion and invasion by increasing the flagellar hydrophobicity. The role of FliB in this process, however, remained enigmatic. In this study, we investigated the properties and mechanisms of FliB from S. enterica in vivo and in vitro. We show that FliB is an S-adenosylmethionine (SAM) dependent methyltransferase, forming a membrane associated oligomer that modifies flagellin in the bacterial cytosol. Using X-band electron paramagnetic resonance (EPR) spectroscopy, zero-field 57Fe Mössbauer spectroscopy, methylation assays and chromatography coupled mass spectrometry (MS) analysis, we further found that FliB contains an oxygen sensitive [4Fe-4S] cluster that is essential for the methyl transfer reaction and might mediate a radical mechanism. Our data indicate that the [4Fe-4S] cluster is coordinated by a cysteine rich motif in FliB that is highly conserved among multiple genera of the Enterobacteriaceae family.