Bull sperm 19S dynein polymerizes brain tubulin into microtubules.

Crude dynein extracted from bull sperm flagella polymerized pure phosphocellulose tubulin isolated from brain tissues into microtubules. This effect was predominantly due to the 19S dynein particle in the extract. ATP stimulated up to five fold the polymerization of brain tubulin by bull sperm dynein. Hydrolysis of ATP was not required since vanadate at a concentration sufficient to block dynein ATPase activity did not interfere with ATP stimulation and because the non hydrolyzable ATP analogue adenylyl (beta-gamma-methylene) diphosphate (AMPPCP) had effects similar to those of ATP. These results suggest that, in addition to hydrolyzing ATP to generate the driving force necessary for microtubule sliding within the axoneme, dynein may also interact with ATP to polymerize tubulin into microtubules.