Autophosphorylation of cGMP-dependent protein kinase is stimulated only by occupancy of one the two cGMP binding sites

AbstractcGMP-Dependent protein kinase contains, per subunit, 2 binding for cGMP. The apparent KD values for site 1 and 2 were 12 and 55 nM. The analogues 8-benzyl-amino-cAMP and N2-monobutyryl-cGMP bind preferentially to site 1 and 2, respectively. Both analogues stimulate autophosphorylation of the enzyme at concentrations at which only half of the phosphotrasferase activity of the enzyme is expressed. Complete expression of the phosphotransferase activity requires a high concentration of each analogue and is accompanied by inhibition of the autophosphorylation reactions. It is concluded that occupancy of site 1 or 2 stimulates autophosphorylation while occupancy of both sites prevents autophosphorylation