Physical Properties of a Purified Cyclic Adenosine 3′:5′-Monophosphate-dependent Protein Kinase from Bovine Heart Muscle

Abstract 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. We conclude that the native enzyme is composed of two catalytic units and one cyclic AMP-binding protein containing two polypeptide chains of equal size.