title: Potentiating effect of calmodulin and catalytic subunit of cyclic AMP-dependent protein kinase on ATP-dependent Ca2+-transport by cardiac sarcolemma.
abstract: Highly purified sarcolemmal membranes were prepared from pig heart homogenates by differential and density gradient centrifugations. The membrane fragments exhibit ATP-dependent Ca2+-transport and Na+/Ca2+-exchange activities. ATP-dependent Ca2+-transport (K0.5Ca2+ = 0.3 microM; Vmax = 4.6 nmol Ca2+.mg protein-1.min-1) is not stimulated by oxalate. Ca2+-uptake is also not supported by p-nitro-phenylphosphate. Preincubation of sarcolemma with MgATP, calmodulin and catalytic subunit of cyclic AMP-dependent protein kinase stimulates active Ca2+-transport 1.8-fold. The effects of calmodulin and catalytic subunit are potentiating rather than additive. A large portion of the Ca2+ additionally accumulated after prephosphorylation of membranes is exchangeable for Na+ via the Na+/Ca2+-exchange system.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology*; D006352:Heart Ventricles / Q000378:metabolism; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism*; D013552:Swine
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D000252:Calcium-Transporting ATPases; D002118:Calcium