PRESENCE OF AN ADENOSINE-5'-TRIPHOSPHATASE DEPENDENT ON 6S-TUBULIN AND CALCIUM-IONS IN RAT-BRAIN MICROTUBULES

An ATPase activity was found in rat brain microtubules prepared by successive cycles of polymerization and depolymerization. On phosphocellulose column chromatography, the ATPase activity was recovered in the fraction eluted with 0.6 M KCl and containing the micro-tubule associated proteins. The ATPase activity was markedly stimulated by the addition of purified brain 6S tubulin, and the stimulation was dependent on the presence of Ca2+ions. Approximately 50 pmol of purified 6S tubulin was required for the maximal stimulation in the presence of 8 μg of microtubule associated proteins. The specific activity was 8 to 13 nmol of ATP hydrolyzed per min per mg of protein at 37°C, and the Km value for ATP was 3×10-5M in the presence of added tubulin. © 1979 by The Journal of Biochemistry.