Abstract
Dynamin was discovered in calf brain tissue as a nucleotide-sensitive microtubule-binding protein with a molecular mass of 100,000. Cross-linked microtubules into bundles and generated force to slide microtubules in vitro. Therefore, it was thought to be a third mechanochemical enzyme, following MAP 1 C and kinesin. Cloning and sequencing of rat brain dynamin complementary DNA revealed that it contained the consensus sequences of GTP-binding proteins.
Studies on dynamin have been difficult because only a small amount of dynamin could be obtained from the brain. I developed a new purification method of dynamin using a small amount of rat brain tissue. It was a highly efficient and very simple procedure, and enabled a further purification step to obtain pure dynamin. I measured both ATPase and GT Pase activities. In the presence of microtubules, ATPase activity was activated 4 times that in their absence (Km 1.0). GTPase activity was activated 170 times (Km 0.07). This suggests that dynamin plays a greater role as GTPase in vivo than as ATPase. The binding manner of Dynamin to micortubules using a quick-freeze deep-etching technique, revealed that dynamin tightly binds to microtubules and decorates the surface of microtubule helically.
