NA+-NA+ EXCHANGE MEDIATED BY (NA++K+)-ATPASE RECONSTITUTED INTO LIPOSOMES - EVALUATION OF PUMP STOICHIOMETRY AND RESPONSE TO ATP AND ADP
NA+-NA+ EXCHANGE MEDIATED BY (NA++K+)-ATPASE RECONSTITUTED INTO LIPOSOMES - EVALUATION OF PUMP STOICHIOMETRY AND RESPONSE TO ATP AND ADP
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DOI：
10.1016/0005-2736(85)90572-3
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
SKOU, JC
中科院分区：
文献类型：
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作者：
CORNELIUS, F;SKOU, JC
(Na当囊外加入ATP时，鲨鱼直肠腺的（+ + K+）-ATP酶在囊内缺乏K+的情况下催化哇巴因敏感的Na+-Na+交换。泡内哇巴因完全抑制交换。将洋地黄毒苷加入囊泡中也是如此。囊泡内注射寡霉素可部分抑制Na+-Na+交换，并呈ATP依赖性。交换伴随着ATP的净水解，表观Km为2.5 μ M。在最适和超最适ATP浓度下，ADP对Na ~+-Na ~+交换无刺激作用，而对Na ~+-Na ~+交换有抑制作用。当测量22 Na的初始流入和流出并同时测定ATP的水解时，发现偶联比为2.8：1.3：1，即对于每摩尔水解的ATP，2.8摩尔Na+被吸收（细胞流出），1.3摩尔Na+被挤出（细胞流入）。产电Na+-Na+交换产生跨膜电位，用荧光探针ANS（8-苯胺基-1-萘磺酸）测量该跨膜电位在脂质体内部（细胞外）为60 mV正。
(Na+ + K+)-ATPase from shark rectal glands reconstituted into lipid vesicles and oriented inside out catalyses an ouabain-sensitive Na+-Na+ exchange in the absence of intravesicular K+ when ATP is added extravesicularly. Intravesicular ouabain inhibited the exchange completely. This was also the case with digitoxigenin added to the vesicles. Intravesicular oligomycin inhibited the Na+-Na+ exchange partly in a fashion which was ATP dependent. The exchange is accompanied by a net hydrolysis of ATP with an apparent Km of 2.5 .mu.M. ADP was found to give no stimulation of the Na+-Na+ exchange, contrarily, ADP inhibited the ATP-dependent exchange of Na+ both at optimal and supraoptimal ATP concentrations. When initial influx and efflux of 22Na was measured and the hydrolysis of ATP concomitantly determined a coupling ratio of 2.8:1.3:1 was found, i.e. 2.8 moles of Na+ were taken up (cellular efflux) and 1.3 moles of Na+ extruded (cellular influx) for each mole of ATP hydrolyzed. The electrogenic Na+-Na+ exchange generated a transmembrane potential which was measured with the fluorescent probe ANS (8-anilino-1-naphthalenesulfonic acid) to be 60 mV positive inside the liposomes (extracellular).