ATPase mechanism of Eg5 in the absence of microtubules: insight into microtubule activation and allosteric inhibition by monastrol.

ABSTRACT: The ATPase mechanism of kinesin superfamily members in the absence of microtubules remains largely uncharacterized. We have adopted a strategy to purify monomeric human Eg5 (HsKSP/Kinesin-5) in the nucleotide-free state (apoEg5) in order to perform a detailed transient state kinetic analysis. We have used steady-state and presteady-state kinetics to define the minimal ATPase mechanism for apoEg5 in the absence and presence of the Eg5-specific inhibitor, monastrol. ATP and ADP binding both occur via a two-step process with the isomerization of the collision complex limiting each forward reaction. ATP hydrolysis and phosphate product release are rapid steps in the mechanism, and the observed rate of these steps is limited by the relatively slow isomerization of the Eg5-ATP collision complex.

SUBMITTER: Cochran JC 

PROVIDER: S-EPMC2270472 | biostudies-literature | 2005 Dec

REPOSITORIES: biostudies-literature