Subunit phosphorylation and activation of skeletal muscle phosphorylase kinase by the cAMP-dependent protein kinase. Divalent metal ion, ATP, and protein concentration dependence.

作者：Cheryl A. Pickett-Gies, Donal A. Walsh · 发表于：Journal of Biological Chemistry · 年份：1985 · DOI：10.1016/s0021-9258(18)89514-x · 被引用次数：52 · 研究领域：Metabolism, Diabetes, and Cancer、Protein Kinase Regulation and GTPase Signaling、Muscle Physiology and Disorders

This report provides a characterization of the effects of varying the concentrations of Mg2+, ATP, phosphorylase kinase, and the cAMP-dependent protein kinase on the activation and phosphorylation of phosphorylase kinase. The results show the following. (a) The Km for MgATP2- for the cAMP-dependent protein kinase-catalyzed phosphorylation is decreased by increasing Mg2+, probably as a consequence of decreasing the free ATP:MgATP2- ratio and increasing free Mg2+. (b) Whereas beta subunit phosphorylation of phosphorylase kinase plays a prominent role in determining its activity, alpha subunit phosphorylation can also modulate activity. (c) The phosphorylation of the alpha subunit, which occurs following the initial cAMP-dependent phosphorylation of the beta subunit, is catalyzed by the cAMP-dependent protein kinase and is not a consequence of EGTA-insensitive (or EGTA-sensitive) autophosphorylation occurring as a result of the enhanced phosphorylase kinase activity. (d) The relationship between subunit phosphorylation and phosphorylase kinase activation is complex and particularly dependent upon concentrations of cAMP-dependent protein kinase and phosphorylase kinase in the activation reaction. The data suggest the possibilities that the pathway of phospho-intermediates involved in the activation process probably varies with the activation conditions, that the efficacy of a specific site to be covalently modified is dependent upon the phosphorylation status of other sites, and ...