Membrane domain localization of pH-regulating transporters in frog skeletal muscle membrane vesicles.
Membrane domain localization of pH-regulating transporters in frog skeletal muscle membrane vesicles.
复制标题
青蛙骨骼肌膜囊泡中 pH 调节转运蛋白的膜域定位。
DOI：
10.1152/ajpcell.1996.271.4.c1367
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Ritucci,NA
中科院分区：
文献类型：
--
作者：
Putnam,RW;Douglas,PB;Ritucci,NA
The distribution of pH-regulating transporters in surface and transverse (T) tubular membrane (TTM) domains of frog skeletal muscle was studied. 2',7'-Bis(carboxyethyl)-5(6)- carboxyfluorescein-loaded giant sarcolemmal vesicles, containing surface membrane, exhibited reversible Na+/H+ exchange. A microsomal vesicle fraction was shown to be enriched in TTM on the basis of high Na(+)-K(+)-ATPase and Mg(2+)-ATPase activity, high ouabain and nitrendipine binding, and low Ca(2+)-ATPase activity. TTM vesicles were well sealed and oriented inside out. Vesicles were loaded with the pH-sensitive dye pyranine. In response to an inwardly directed Na+ gradient, vesicles displayed virtually no alkalinization unless monensin was present. No pH response to an imposed Na+ gradient was seen regardless of the direction of the pH gradient across the vesicles, after phosphorylation of the vesicles with protein kinase C, or when exposed to guanosine 5'-O-(3-thiotriphosphate). In the presence of CO2, addition of Na+ or Cl- had no effect on vesicle pH. These data indicate that the TTM lacks functional pH-regulating transporters [Na+/H+ and (Na+ + HCO3-)/Cl- exchangers], suggesting that pH-regulating transporters are localized only to the surface membrane domain in frog muscle.
