Stimulation by Tubulin of an Adenylate Cyclase from Murine Plasmacytoma

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Abstract
Different brain tubulin preparations stimulated membrane-bound adenylate cyclase from the murine plasmacytoma MOPC 173. Purified tubulin devoid of microtubule-associated proteins and of nucleoside diphosphate kinase activity was responsible for this stimulation. Activation of the basal adenylate cyclase activity occurred in < 2 min at 32.degree. C and was amplified by a 4.degree. C preincubation of tubulin with plasma membranes. Tubulin affected the Km and the V of the enzyme and was associated with the membrane during the activation phenomenon. Tubulin was more active on the basal adenylate cyclase activity than that stimulated by fluoride or guanosine 5''-[.beta.,.gamma.-imido]triphosphate. GTP has no effect on the tubulin-stimulated enzyme.