EFFECT OF ATP ON BINDING OF CA2+ CALMODULIN-DEPENDENT PROTEIN KINASE-II WITH CALMODULIN

Binding of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) with calmodulin was directly determined by the poly(ethylene glycol) precipitation method. Calmodulin bound to CaM kinase II alpha and beta polypeptides in a molar ratio of about 1 : 1 in the presence of ATP, but the binding was reduced in the absence of ATP. Affinity of CaM kinase II for calmodulin increased in the presence of ATP and the autophosphorylation was observed under the conditions. ADP and adenosine beta, gamma-imidoadenosine 5'-triphosphate, hydrolysis resistant analogues, also increased the binding of CaM kinase II with calmodulin. CaM kinase II substrate syntide 2 did not increase the binding of the kinase with calmodulin. These findings indicate that the affinity of CaM kinase II for calmodulin and the amount of calmodulin bound to the kinase increase by the binding of ATP.