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Biochemistry. 2006 Oct 3;45(39):11790-8.

The FliN-FliH interaction mediates localization of flagellar export ATPase FliI to the C ring complex.

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  • 1Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA. jmcmurr1@kennesaw.edu

Abstract

FliH regulates the flagellar export ATPase FliI, preventing nonproductive ATP hydrolysis. FliH has been shown to stably associate with the C ring protein FliN. Analysis of this complex reveals that FliH is required for FliI localization to the C ring, and thus FliH not only inhibits FliI ATPase activity but also may act to target FliI to the basal body. Quantitative binding studies revealed a KD of 110 nM for FliH binding to FliN. The KD for FliH binding of a FliN variant from a temperature-sensitive nonflagellate fliN point mutant was determined to be 270 nM, suggesting a molecular explanation for its phenotype. Another variant FliN from a temperature-sensitive mutant with a different phenotype displayed binding with an intermediate affinity. Weak export activity in a fliN null mutant was greatly increased by overproduction of FliI, mimicking a previously observed FliH bypass effect and supporting the conclusion that FliN-FliH binding is important for localization of FliI to the C ring and thus the membrane-embedded export apparatus beyond. A model incorporating the present findings is presented.

PMID:
17002279
[PubMed - indexed for MEDLINE]
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