Properties of the 23,000-Da phosphoproteins in cardiac sarcolemma and sarcoplasmic reticulum.
The calmodulin- and cAMP-dependent protein kinase-mediated phosphorylations of isolated sarcolemma and sarcoplasmic reticulum vesicles have been compared. Similarities in the calmodulin-mediated phosphorylation of the sarcolemma and sarcoplasmic reticulum 23,000-Da phosphoproteins included their Mg2+, Na+, Ca2+, and calmodulin sensitivities, as well as the size of their dissociated subunits. In contrast, a number of differences between these phosphoproteins were indicated in their sensitivity to detergents (Triton X-100 and sodium dodecyl sulfate) and calmodulin antagonists (R24571 and trifluoperazine). Furthermore, in contrast to the sarcoplasmic reticulum phosphoprotein, the sarcolemma phosphoprotein could not be affinity labeled with 125I-calmodulin. While these results indicate the probable chemical similarity of the sarcolemma and sarcoplasmic reticulum 23,000-Da phosphoproteins, they also indicate there are differences in the lipid/phosphoprotein interactions in these two membranes.
D000408:Alamethicin / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D003902:Detergents / Q000494:pharmacology; D004285:Dogs; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D002147:Calmodulin; D003902:Detergents; D009124:Muscle Proteins; D010750:Phosphoproteins; D000408:Alamethicin; D000242:Cyclic AMP; D011494:Protein Kinases