Regulation of protein synthesis in rabbit reticulocyte lysates: effect of of Ca²⁺, Mg²⁺, and Mn²⁺ on self-phosphorylation and heterophosphorylation catalyzed by the heme-regulated and double-stranded-RNA-activated protein kinases

The influence of divalent cations Mg²⁺, Mn²⁺, and Ca²⁺ on the cyclic-AMP-independent protein kinases of the heine-regulated and double-stranded-RNA-activated translational inhibitory protein kinases on self-phosphorylation and heterophosphorylation of the substrate (the 38 000-dalton subunit of initiation factor eIF-2) has been examined, Results show that Mg²⁺, Mn²⁺, and Ca²⁺ affect the activities of these enzymes in the following fashion. Mg²⁺ supports both self-phosphorylation and heterophosphorylation efficiently. Mn²⁺ on the other hand supports self-phosphorylation but to a lesser degree the heterophosphorylation, Ca²⁺ promotes neither self-phosphorylation nor hetero-phosphorylation.