Characterization of subfractions from purified sarcolemma of canine left ventricle.
Three membrane fractions were studied from canine myocardial left ventricle (LV); crude, light vesicle, and enriched sarcolemma. The percent of the total yield of membrane protein was 99.3 +/- 0.2% for the crude fraction, 0.4 +/- 0.1% for the light vesicle fraction, and 0.3 +/- 0.03% for the purified fraction. Sodium, potassium-ATPase activity in the purified fraction (100 +/- 10.8 mumol Pi/h/mg) was five fold more concentrated than in the light vesicle fraction (18.5 +/- 1.85 mumol Pi/h/mg), and nineteen fold more than in the crude fraction (5.29 +/- 0.57 mumol Pi/h/mg). beta-Adrenergic receptors were 8-fold enriched in the purified fraction (1006 +/- 219 vs 132 +/- 13 fmol/mg in the crude fraction) and 4-fold enriched in the light vesicle fraction (497 +/- 152 fmol/mg). Adenylate cyclase activity was enriched by only 13 to 17-fold in the purified fraction, and only 2 to 4-fold in the light vesicle fraction. The percent of the total beta-adrenergic receptors per gram wet weight was 94 +/- 20% for the crude fraction, 2.1 +/- 0.4% for the light vesicle fraction, and 3.8 +/- 0.7% for the purified fraction. When alamethicin was used to uncover latent enzyme activity, beta-adrenergic receptor density was not affected, but Na+,K(+)-ATPase and adenylate cyclase activity were enhanced in each membrane fraction studied. The surprising finding was that Na+,K(+)-ATPase activity was enriched to the same extent as the beta-adrenergic receptor density in the light vesicle fraction. One potential explanation is that the light vesicle fraction is located in a specialized region of the plasma membrane.
Vatner
D E
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Department of Pediatrics, Harvard Medical School, Massachusetts General Hospital, Boston 02114.
D000262:Adenylyl Cyclases / Q000032:analysis; D000818:Animals; D002458:Cell Fractionation / Q000379:methods; D004285:Dogs; D005260:Female; D006352:Heart Ventricles / Q000737:chemistry* / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D012508:Sarcolemma / Q000737:chemistry* / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
D011943:Receptors, Adrenergic, beta; D000262:Adenylyl Cyclases; D000254:Sodium-Potassium-Exchanging ATPase