Bovine lung cyclic GMP-dependent protein kinase exhibits two types of specific cyclic GMP-binding sites

Cyclic GMP-dependent protein kinase from bovine lung exhibits two distinct and specific binding sites for cyclic GMP. Cyclic GMP bound to Site II dissociates very rapidly (t 1/2 less than 10 s at 0 or 30 degrees C) and requires the presence of ammonium sulfate in the wash buffer for its detection using cellulose ester filters. Both sites are highly specific for cyclic GMP and show affinities for cyclic GMP in the physiological range (less than 1 microM at 30 degrees C). Only cyclic GMP bound to the high affinity site (Site I) correlated with stimulation of histone kinase activity using arginine-rich histone as the substrate; however, both sites were involved with stimulation of histone kinase activity using mixed histones as the substrate. Stimulation of autophosphorylation by cyclic GMP was closely correlated with the binding of cyclic GMP to Site I.