Physical properties of a purified cyclic adenosine 3':5' monophosphate dependent protein kinase from bovine heart muscle

The physical properties of a homogeneous preparation of cyclic adenosine 3':5' monophosphate (cyclic AMP) dependent protein kinase and its subunits were studied using gel filtration, sucrose density gradient sedimentation, and analytical ultracentrifugation. Molecular weights of the holoenzyme and its cyclic AMP binding and phosphotransferase (catalytic) components were 174,000, 98,000, and 38,000, respectively. Frictional and axial ratios were 1.6 and 12 for both the holoenzyme and the cyclic AMP binding protein and 1.1 and 3 for the catalytic component. It is concluded that the native enzyme is composed of two catalytic units and one cyclic AMP binding protein containing two polypeptide chains of equal size.