Display Settings:

Format

Send to:

Choose Destination
Proc Natl Acad Sci U S A. 2010 Jun 22;107(25):11295-300. doi: 10.1073/pnas.1001383107. Epub 2010 Jun 2.

FlhA provides the adaptor for coordinated delivery of late flagella building blocks to the type III secretion system.

Author information

  • 1Biochemie-Zentrum der Universität Heidelberg, INF328, 69120 Heidelberg, Germany.

Abstract

Flagella are the bacterial organelles of motility and can play important roles in pathogenesis. Flagella biosynthesis requires the coordinated export of huge protein amounts from the cytosol to the nascent flagellar structure at the cell surface and employs a type III secretion system (T3SS). Here we show that the integral membrane protein FlhA from the gram-positive bacterium Bacillus subtilis acts as an adaptor for late export substrates at the T3SS. The major filament protein (flagellin) and the filament-cap protein (FliD) bind to the FlhA cytoplasmic domain (FlhA-C) only in complex with their cognate chaperones (FliS and FliT). To understand the molecular details of these interactions we determined the FlhA-C crystal structure at 2.3 A resolution. FlhA-C consists of an N-terminal linker region, three subdomains with a novel fold, and a disordered region essential for the adaptor function. We show that the export protein FliJ associates with the linker region and modulates the binding properties of FlhA-C. While the interaction of FliD/FliT is enhanced, flagellin/FliS is not affected. FliJ also keeps FliT associated with FlhA-C and excess of FliT inhibits binding of FliD/FliT, suggesting that empty FliT chaperones stay associated with FliJ after export of FliD. Taken together, these results allow to propose a model that explains how the T3SS may switch from the stoichiometric export of FliD to the high-throughput secretion of flagellin.

PMID:
20534509
[PubMed - indexed for MEDLINE]
PMCID:
PMC2895114
Free PMC Article

Images from this publication.See all images (5)Free text

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk