Colchicine-binding Protein from Human Platelets and Its Effect on Muscle Myosin and Platelet Myosin-like Thrombosthenin-M

A colchicine-binding protein was isolated from sonically treated platelets by ammonium sulfate precipitation (40 to 50% saturation), followed by elution from DEAE-Sephadex A-50 with a KCl gradient. Disc electrophoresis revealed one major protein band. This protein bound 0.042 µmole of colchicine per 100 mg; it lacked ATPase activity, but markedly altered the cation requirements for the ATPase activity of both muscle myosin and thrombosthenin-M, and when added to either muscle myosin or thrombosthenin-M, produced a rise in relative viscosity which fell sharply upon addition of ATP.