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ATP-induced FliI hexamerization facilitates bacterial flagellar protein export
Ken-Ichi Kazetani1, Tohru Minamino, Tomoko Miyata
1Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
Biochemical and Biophysical Research Communications
|August 12, 2009
Summary
ATP binding drives bacterial flagellar protein export by forming FliI ATPase hexamers. ATP hydrolysis and release destabilize the hexamer, coupling assembly to export initiation.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- The bacterial flagellar type III secretion system (T3SS) requires the FliI ATPase for energy.
- FliI forms a homo-hexamer to facilitate protein export, but the mechanism linking hexamerization to function is unclear.
Purpose of the Study:
- To investigate the role of ATP binding and hydrolysis in FliI hexamerization.
- To determine how FliI assembly and disassembly influence flagellar protein export.
Main Methods:
- Analysis of FliI ring formation using wild-type and mutant variants.
- Assessment of hexamerization in the presence of ATP and non-hydrolyzable ATP analogs.
- Evaluation of flagellar protein export capabilities of FliI mutants.
Main Results:
- ATP binding, not hydrolysis, induces FliI hexamerization.
- Non-hydrolyzable ATP analogs and the catalytic mutant FliI(E221Q) promoted hexamer formation.
- Reduced ATP binding affinity abolished ring formation.
- FliI(E221Q) partially facilitated protein export independently of the FliH regulator.
Conclusions:
- FliI hexamerization is primarily regulated by ATP binding.
- The assembly-disassembly cycle of FliI, driven by ATP binding and hydrolysis, is crucial for initiating flagellar protein export.
- FliI's function is coupled to its conformational changes during the ATPase cycle.
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