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Updated: Oct 20, 2026

Investigating Flagella-Driven Motility in Escherichia coli by Applying Three Established Techniques in a Series
Published on: May 10, 2020
Interaction of FliI, a component of the flagellar export apparatus, with flagellin and hook protein
1Departamento de Genética Molecular, Instituto de Fisiología Celular, UNAM, Apdo. Postal 70-600, 04510, México D.F., Mexico.
Abstract:
FliI is a key component of the flagellar export apparatus in Salmonella typhimurium. It catalyzes the hydrolysis of ATP which is necessary for flagellar assembly. Affinity blotting experiments showed that purified flagellin and hook protein, two flagellar axial proteins, interact specifically with FliI. The interaction of either of the two proteins with FliI, increases the intrinsic ATPase activity. The presence of either flagellin or hook protein stimulates ATPase activity in a specific and reversible manner. A Vmax of 0.12 nmol Pi min-1 microgram-1 and a Km for MgATP of 0.35 mM was determined for the unstimulated FliI; the presence of flagellin increased the Vmax to 0.35 nmol Pi min-1 microgram-1 and the Km for MgATP to 1.1 mM. The stimulation induced by the axial proteins was fully reversible suggesting a direct link between the catalytic activity of FliI and the export process.
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