Protein phosphokinases of chick muscle: Changes during embryonic development

Abstract

Protein phosphorylation is a widespread phenomenom [l] involving, among others, such distinct cell functions as enzyme conversions [2] , changes ’ in membrane permeability [3], and regulation of RNA transcription [4]. Protein phosphokinases with different substrate specificity have been found [5,6] and histone phosphorylation has been particularly implicated in gene activation through increased template activity [7]. In fact, the increased rate of nucleoprotein phosphorylation is concomitant with an active cell division like that occurring e.g. in regenerating liver [ 81 , in unilaterally nephrectomized kidney and fast growing tumoral ascites cells [9] , and the developing mammary gland [lo]. Protein kinase from rabbit muscle phosphorylates several proteins, including glycogen synthetase [ 5, 1 l] . Since the pattern during embryonic development of chick muscle glycogen synthetase kinase has been described [ 121, it was interesting to know the patterns with the other substrates. In fact, eventual differences would indicate that protein kinases with changing functions might be present during muscle differentiation. It is the purpose of this communication to report