Open AccessFliH and FliI ensure efficient energy coupling of flagellar type III protein export in Salmonella
Author(s) -
Minamino Tohru,
Kinoshita Miki,
Inoue Yumi,
Morimoto Yusuke V.,
Ihara Kunio,
Koya Satomi,
Hara Noritaka,
Nishioka Noriko,
Kojima Seiji,
Homma Michio,
Namba Keiichi
Publication year - 2016
Publication title -
microbiologyopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.881
H-Index - 36
ISSN - 2045-8827
DOI - 10.1002/mbo3.340
Subject(s) - flagellum , biology , complementation , mutant , microbiology and biotechnology , chaperone (clinical) , gene , genetics , medicine , pathology
For construction of the bacterial flagellum, flagellar proteins are exported via its specific export apparatus from the cytoplasm to the distal end of the growing flagellar structure. The flagellar export apparatus consists of a transmembrane (TM) export gate complex and a cytoplasmic ATP ase complex consisting of FliH, FliI, and FliJ. FlhA is a TM export gate protein and plays important roles in energy coupling of protein translocation. However, the energy coupling mechanism remains unknown. Here, we performed a cross‐complementation assay to measure robustness of the energy transduction system of the export apparatus against genetic perturbations. Vibrio FlhA restored motility of a Salmonella Δ flhA mutant but not that of a Δ fliH‐fliI flhB(P28T) Δ flhA mutant. The flgM mutations significantly increased flagellar gene expression levels, allowing Vibrio FlhA to exert its export activity in the Δ fliH‐fliI flhB(P28T) Δ flhA mutant. Pull‐down assays revealed that the binding affinities of Vibrio FlhA for FliJ and the FlgN–FlgK chaperone–substrate complex were much lower than those of Salmonella FlhA. These suggest that Vibrio FlhA requires the support of FliH and FliI to efficiently and properly interact with FliJ and the FlgN–FlgK complex. We propose that FliH and FliI ensure robust and efficient energy coupling of protein export during flagellar assembly.