Human erythrocyte proteins associated with adenosine 3',5'-cyclic monophosphate action

Two adenosine 3',5'-cyclic monophosphate (cyclic-AMP)-binding protein factors (molecular weight 230,000) have been partially purified from human erythrocytes. One of these proteins seems to be different from the cyclic-AMP-binding component of the cyclic-AMP-dependent protein kinases. These protein factors are also capable of binding adenosine. We present data also on two forms of cyclic-AMP-dependent protein kinases (ATP: protein phosphotransferase, EC 2.7.1.37) partially purified from the cytosol of normal human erythrocytes. Kinase I has been classified as type I enzyme on the basis of its activation when preincubated with protamine, histone or NaCl. The substrate specificities of the two kinases and many of their kinetic parameters are rather similar. Their subunit structure is reminiscent of that of kinases obtained from other sources. The catalytic subunit of both enzymes reversibly cross-react with the regulatory subunit of kinase I from the rabbit red blood cell.