MICROTUBULE DYNAMICS MODULATED BY GUANOSINE TRIPHOSPHATE HYDROLYSIS ACTIVITY OF BETA-TUBULIN

Microtubule dynamic instability underlies many cellular functions, inc luding spindle morphogenesis and chromosome movement. The role of guan osine triphosphate (GTP) hydrolysis in dynamic instability was investi gated by introduction of four mutations into yeast beta-tubulin at ami no acids 103 to 109, a site thought to participate in GTP hydrolysis. Three of the mutations increased both the assembly-dependent rate of G TP hydrolysis and the average length of steady-state microtubules over time, a measure of dynamic instability. The fourth mutation did not s ubstantially affect the rate of GTP hydrolysis or the steady-state mic rotubule lengths. These results demonstrate that the rate of GTP hydro lysis can modulate microtubule length and hence dynamic instability.