FliS/flagellin/FliW heterotrimer couples type III secretion and flagellin homeostasis

Sci Rep. 2018 Aug 1;8(1):11552. doi: 10.1038/s41598-018-29884-8.


Flagellin is amongst the most abundant proteins in flagellated bacterial species and constitutes the major building block of the flagellar filament. The proteins FliW and FliS serve in the post-transcriptional control of flagellin and guide the protein to the flagellar type III secretion system (fT3SS), respectively. Here, we present the high-resolution structure of FliS/flagellin heterodimer and show that FliS and FliW bind to opposing interfaces located at the N- and C-termini of flagellin. The FliS/flagellin/FliW heterotrimer is able to interact with FlhA-C suggesting that FliW and FliS are released during flagellin export. After release, FliW and FliS are recycled to execute a new round of post-transcriptional regulation and targeting. Taken together, our study provides a mechanism explaining how FliW and FliS synchronize the production of flagellin with the capacity of the fT3SS to secrete flagellin.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacillus subtilis / metabolism*
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Crystallography, X-Ray
  • Homeostasis
  • Models, Molecular
  • Protein Conformation
  • Protein Multimerization*
  • Type III Secretion Systems / chemistry*
  • Type III Secretion Systems / metabolism*


  • Bacterial Proteins
  • Type III Secretion Systems