Components of purified sarcolemma from porcine skeletal muscle

James R. Mickelson, Charles F. Louis

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Sarcolemmal membranes were isolated from porcine skeletal muscle by modifications of a LiBr-extraction technique. Latency determinations of acetylcholinesterase, ouabainsensitive p-nitrophenylphosphatase, [3H]ouabain binding, and (Na+ + K+)-ATPase activities indicated that 65-76% of the membranes were sealed inside-out vesicles. The preparations were enriched in cholesterol and phospholipid, and demonstrated adenylate cyclase activity and both cAMP and cGMP phosphodiesterase activities. An indication of the purity of this fraction was that the Ca2+-ATPase activity (0.13 μmol Pi mg-1 min-1 at 37 °C) was 3.8% of that of porcine skeletal muscle sarcoplasmic reticulum preparations. Pertussis toxin specifically catalyzed the ADP-ribosylation of a Mr 41,000 sarcolemmal protein, indicating the presence of the inhibitory guanine nucleotide regulatory protein of adenylate cyclase, Ni. An endogenous ADP-ribosyl-transferase activity, with several membrane protein substrates, was also demonstrated. The addition of exogenous cAMP-dependent protein kinase or calmodulin promoted the phosphorylation of a number of sarcolemmal proteins. The calmodulin-dependent phosphorylation exhibited an approximate K 1 2 for Ca2+ of 0.5 μm, and an approximate K 1 2 for calmodulin of 0.1 μm. 125I-Calmodulin affinity labeling of the sarcolemma, using dithiobis(succinimidyl propionate), demonstrated the presence of Mr 160,000 and 280,000 calmodulin-binding components in these membranes. These results demonstrate that this porcine preparation will be valuable in the study of skeletal muscle sarcolemmal ion transport, protein and hormonal receptors, and protein kinasecatalyzed phosphorylation.

Original languageEnglish (US)
Pages (from-to)112-126
Number of pages15
JournalArchives of Biochemistry and Biophysics
Issue number1
StatePublished - Oct 1985

Bibliographical note

Funding Information:
i This work was funded, in part, by grants from the Muscular Dystrophy Association, the Minnesota Swine Center, and NIH GM-31382. A preliminary report of some of this material has already appeared [J. R. Mickelson, E. M. Gallant, and C. F. Louis (1984) Biophys J. 45, 79a]. * Postdoctoral Fellow of the Muscular Association. To whom correspondence addressed.


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