Calmodulin binding and protein phosphorylation in adrenal medulla coated vesicles

Abstract

Coated vesicles from bovine adrenal medulla contained clathrin and major detergent‐insoluble polypeptides of 120‐100, 51 and 49 kDa. Intact coated vesicles and vesicles lacking clathrin light chains were bound by immobilized calmodulin in the presence of Ca²⁺. Clathrin in the form of 700 Å cages was not bound. The calmodulin binding components in intact coated vesicles are therefore contributed by the enclosed vesicle or by the 120‐100, 50 or 49 kda polypeptides. The 51 kDa component incorporated ³²P_i from labelled ATP by an endogenous kinase activity; no other coat or vesicle membrane protein was phosphorylated in vitro, either by intrinsic or exogenous kinases.