Modulation of the Phosphorylation and Activity of Calcium/Calmodulin‐Dependent Protein Kinase II by Zinc

Calcium/calmodulin‐dependent protein kinase II (CaMPK‐II) is a key regulatory enzyme in living cells. Modulation of its activity, therefore, could have a major impact on many cellular processes. We found that Zn2+ has multiple functional effects on CaMPK‐II. Zn2+ generated a Ca2+/CaM‐independent activity that correlated with the autophosphorylation of Thr286, inhibited Ca2+/CaM binding that correlated with the autophosphorylation of Thr306, and inhibited CaMPK‐II activity at high concentrations that correlated with the autophosphorylation of Ser279. The relative level of autophosphorylation of these three sites was dependent on the concentration of zinc used. The autophosphorylation of at least these three sites, together with Zn2+ binding, generated an increased mobility form of CaMPK‐II on sodium dodecyl sulfate gels. Overall, autophosphorylation induced by Zn2+ converts CaMPK‐II into a different form than the binding of Ca2+/CaM. In certain nerve terminals, where Zn2+ has been shown to play a neuromodulatory role and is present in high concentrations, Zn2+ may turn CaMPK‐II into a form that would be unable to respond to calcium signals.