Association of the type I regulatory subunit of cAMP-dependent protein kinase with cardiac myocyte sarcolemma.
Cardiac sarcolemmal vesicles purified from bovine and porcine left ventricles contained approximately 45 pmol of cAMP-dependent protein kinase (PKA) regulatory (R) subunit per milligram membrane protein based on [3H]cAMP-binding activity. Less than 26% of this activity was complexed with the catalytic subunit forming the type H holoenzyme of PKA. The remainder was contributed by the free type I R subunit (RI). Purification of sarcolemma with buffers containing 0.15 M NaCl instead of 0.75 M NaCl did not affect the ratio of RI to RII, nor did it increase the total amount of membrane-associated cAMP-binding or kinase activity. Canine, rabbit, and rat heart sarcolemma also contained RI, but in highly varying proportions compared with RII as determined by 8-N3-[32P]cAMP photoaffinity labeling. Analysis of sarcolemmal vesicles from isolated porcine ventricular myocytes demonstrated that this cell type was the source of the membrane-associated RI. The results indicate that sarcolemmal RI must be considered as a factor that could influence the varied responses of the heart to agents that elevate intracellular cAMP.
Robinson
M L
ML
Department of Biochemistry and Molecular Biology, University of North Dakota School of Medicine, Grand Forks 58202-9037, USA.
Wallert
M A
MA
Reinitz
C A
CA
Shabb
J B
JB
D000251:Adenosine Triphosphatases / Q000032:analysis; D000345:Affinity Labels; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis; D002417:Cattle; D002852:Chromatography, Ion Exchange; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis* / Q000737:chemistry; D004285:Dogs; D006352:Heart Ventricles; D009206:Myocardium / Q000201:enzymology*; D011817:Rabbits; D051381:Rats; D012508:Sarcolemma / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013045:Species Specificity; D013552:Swine
D000345:Affinity Labels; D017868:Cyclic AMP-Dependent Protein Kinases; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase