Calcium-activated protein kinase from soluble and membrane fractions of maize coleoptiles

This paper describes the results of experiments in which phenyl Sepharose was used to partially purify Ca2(+)-activated protein kinase (CPK) from maize soluble and membrane-solubilized proteins. It is shown that CPK has very similar properties to Ca2(+)-activated, calmodulin independent protein kinase from other plant tissues, and that chromatography on phenyl Sepharose resolves two closely related forms of CPK from both soluble and membrane-solubilized proteins. The amount of each of these forms differs in the two fractions, and it is suggested that the kinase requiring EGTA for elution from phenyl Sepharose at high pH may be either a non-proteolitically digested form or an acylated form of CPK.