Cornelius F, Skou J C
Biochim Biophys Acta. 1985 Aug 27;818(2):211-21. doi: 10.1016/0005-2736(85)90572-3.
(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 microM. 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).
重构到脂质小泡中且呈外翻取向的鲨鱼直肠腺（钠 + 钾）-ATP 酶，在囊泡外添加 ATP 且囊泡内无钾离子时，催化哇巴因敏感的钠 - 钠交换。囊泡内的哇巴因完全抑制该交换。向囊泡中添加洋地黄毒苷时情况也是如此。囊泡内的寡霉素以一种依赖 ATP 的方式部分抑制钠 - 钠交换。该交换伴随着 ATP 的净水解，其表观 Km 为 2.5 μM。发现 ADP 对钠 - 钠交换无刺激作用，相反，在最佳和超最佳 ATP 浓度下，ADP 均抑制依赖 ATP 的钠交换。当测量 22Na 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，即每水解 1 摩尔 ATP，有 2.8 摩尔的钠离子被摄取（细胞外流），1.3 摩尔的钠离子被排出（细胞内流）。由生电钠 - 钠交换产生的跨膜电位，用荧光探针 ANS（8 - 苯胺基 - 1 - 萘磺酸）测量，结果显示脂质体内部（细胞外）为正 60 mV。
