Resolution of Ca²⁺—calmodulin‐activated protein kinase from wheat germ

Abstract

A soluble Ca 2+ ‐ and Ca 2+ —calmodulin‐activated protein kinase was partially purified from wheat germ. The phosphorylation of histones and casein catalyzed by this enzyme is largely Ca 2+ ‐dependent. After repeated gel filtration of the protein kinase in the presence of 1 mM EGTA, the phosphorylation of casein and histones by the enzyme is activated 3‐fold and up to 16‐fold, respectively, by added calmodulin (12.5 μM). Such activation of the protein kinase by calmodulin is Ca 2+ ‐dependent. The protein kinase binds to calmodulin—Sepharose 4B in a Ca 2+ ‐dependent fashion. This type of Ca 2+ ‐activated protein kinase may be involved in stimulus—response coupling in plants.