Department of Pharmacology, University of California, San Francisco 94143.
Tubulin is a GTPase that hydrolyzes its bound nucleotide triphosphate after it becomes incorporated into a microtubule. The only known consequence of nucleotide hydrolysis is that it increases the dissociation rate of tubulin from the end of the microtubule by 2 orders of magnitude. In this study, we investigated whether microtubules composed of tubulin-GMPCPP (guanylyl alpha,beta-methylenediphosphate) (a very slowly hydrolyzed GTP analog) or tubulin-GDP exhibit additional structural or functional differences. We show that tubulin-GMPCPP microtubules are significantly stiffer than tubulin-GDP microtubules and have a 21% shallower protofilament twist angle. We also find that kinesin, a microtubule-based motor protein, transports tubulin-GMPCPP microtubules at approximately 30% faster rates than tubulin-GDP microtubules. These findings suggest that growing microtubule ends, which are thought to be composed of tubulin-GTP, may have different structural and mechanical properties from the remainder of the microtubule polymer.
PMID: 7916345, UI: 94375488
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