Horisberger J D, Jaunin P, Reuben M A, Lasater L S, Chow D C, Forte J G, Sachs G, Rossier B C, Geering K
Institut de Pharmacologie et de Toxicologie de l'Université, Lausanne, Switzerland.
J Biol Chem. 1991 Oct 15;266(29):19131-4.
Na,K-ATPase and H,K-ATPase are the only members of the P-type ATPases in which a glycosylated beta-subunit is part of the purified active enzyme. In this study, we have followed the synthesis and the posttranslational processing of the beta-subunit of H,K-ATPase (beta HK) in Xenopus oocytes injected with beta HK cRNA and have tested whether it can act as a surrogate for the beta-subunit of Na,K-ATPase (beta NaK) to support the functional expression of Na,K-pumps. In Xenopus oocytes, beta HK is processed from an Endo H-sensitive 51-kDa coreglycosylated form to an Endo H-resistant 71-kDa fully glycosylated form. Similar to beta NaK, beta HK can stabilize and increase the trypsin resistance of alpha-subunits of Na,K-ATPase (alpha NaK). Finally, expression of beta HK together with alpha NaK leads to an increased number of ouabain binding sites at the plasma membrane accompanied by an increased Rb+ uptake and Na,K-pump current. Our data suggest that beta HK, similar to beta NaK, can assemble to alpha NaK, support the structural maturation and the intracellular transport of catalytic alpha NaK, and ultimately form active alpha NaK-beta HK complexes with Na,K-pump transport properties.
钠钾ATP酶和氢钾ATP酶是P型ATP酶中仅有的成员，其糖基化的β亚基是纯化活性酶的一部分。在本研究中，我们追踪了注射βHK编码RNA的非洲爪蟾卵母细胞中氢钾ATP酶β亚基（βHK）的合成及翻译后加工过程，并测试了它是否能替代钠钾ATP酶β亚基（βNaK）来支持钠钾泵的功能表达。在非洲爪蟾卵母细胞中，βHK从对内切糖苷酶H敏感的51 kDa核心糖基化形式加工为对内切糖苷酶H有抗性的71 kDa完全糖基化形式。与βNaK相似，βHK能稳定钠钾ATP酶α亚基（αNaK）并增加其对胰蛋白酶的抗性。最后，βHK与αNaK共同表达导致质膜上哇巴因结合位点数量增加，同时铷离子摄取和钠钾泵电流增加。我们的数据表明，βHK与βNaK相似，能够与αNaK组装，支持催化性αNaK的结构成熟和细胞内运输，并最终形成具有钠钾泵运输特性的活性αNaK-βHK复合物。
