Adenosine 3', 5'-Monophosphate-Dependent Membrane Phosphorylation
A Possible Mechanism for the Control of Microsomal Calcium Transport in Heart Muscle
The role of cyclic adenosine 3', 5'-monophosphate (AMP) in the control of microsomal calcium ion (Ca2+) transport was studied in microsomes prepared from rabbit heart. These cardiac microsomes contained intrinsic cyclic AMP-dependent protein kinase activity that phosphorylated serine residues in a microsomal protein component with a molecular weight of about 20,000 (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Intrinsic phosphoprotein phosphatase activity of the microsomal membranes resulted in rapid dephosphorylation of these residues. Microsomes phosphorylated in the presence of 1 x 10-6M cyclic AMP exhibited enhanced Ca2+ uptake. We conclude that reversible phosphorylation of microsomal membranes may be an important mechanism for regulation of microsomal Ca2+ transport by cyclic AMP.
- Received December 20, 1973.
- Accepted May 3, 1974.
- © 1974 American Heart Association, Inc.