Effects of 60Co gamma irradiation on the polymerization of microtubules in vitro

Microtubules have been shown to depolymerize in vitro into a high-molecular-weight aggregate and a 6S component. Irradation of these components separately has indicated that the 6S component is preferentially damaged. This was shown by a reduction in the extent of polymerization following reconstitution of the irradiated and control fractions. The irradiation had no apparent effect on either protein kinase activity or on [14C]-colchicine binding ability. In addition, irradiation of depolymerized microtubules at various protein concentrations has demonstrated that the 6S tubulin is also preferentially damaged in the presence of the high-molecular-weight component