Phosphorylation of muscle proteins by cyclic adenosine 3′,5′-monophosphate-dependent protein kinase from muscle

Abstract

Tissue-specific substrates for a cyclic AMP-dependent protein kinase from bovine tracheal smooth muscle have been partially characterized. The substrates are phosphorylated by purified smooth muscle kinase or by kinases found in crude extracts of bovine smooth, skeletal, and cardiac muscle. The substrates derived from and phosphorylated by smooth muscle protein kinase have a molecular weight of approximately 70 000, as determined by disc gel electrophoresis in the absence of sodium dodecyl sulfate and of approx. 20 000–25 000 when electrophoresed in the presence of sodium dodecyl sulfate. It appears that there are a liminated number of substrates for the smooth muscle cyclic AMP-dependent protein kinase.