期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1971
卷号：68
期号：10
页码：2444-2447
DOI：10.1073/pnas.68.10.2444
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Two cAMP-dependent protein kinases purified from rabbit skeletal muscle were shown to bind the same amount of cAMP per unit of enzyme activity at several concentrations of this nucleotide. A preparation containing both of these kinases was separated into catalytic (C) and regulatory (R) subunit fractions in the presence of cAMP, the regulatory subunit being obtained as an R{middle dot}cAMP complex. Addition of increasing amounts of the R{middle dot}cAMP complex to the holoenzyme (RC) increased the concentration of cAMP required for half-maximal activity of the enzyme. cAMP was liberated from the R{middle dot}cAMP complex in the presence of added catalytic subunit in a reaction that was facilitated by Mg2+, ATP, and warming. These findings are presented in support of a model for activation of the protein kinase by cAMP. The possibility that excess regulatory subunit may serve as a sink for intracellular cAMP is also discussed. It is shown that cAMP bound to the R subunit is not a substrate for the cAMP phosphodiesterase.
