Jaisser F, Horisberger J D, Rossier B C
Institut de Pharmacologie et de Toxicologie, Lausanne, Switzerland.
Ann N Y Acad Sci. 1992 Nov 30;671:113-9. doi: 10.1111/j.1749-6632.1992.tb43789.x.
We recently cloned the alpha 1 and the beta 1 and beta 3 subunits of the Na,K-ATPase of the toad Bufo marinus. To investigate possible functional differences between beta 1 and beta 3, we studied the potassium activation of Na-K pumps expressed in the oocyte of Xenopus laevis. Na-K pump activity was measured as K(+)-induced current in voltage-clamped oocytes. We could take advantage of the relative resistance to ouabain conferred by the Bufo alpha subunit to study specifically the exogenously expressed Na-K pumps after inhibition of the ouabain-sensitive endogenous Xenopus Na-K pumps. Coinjection of Bufo alpha 1 subunit cRNA with either beta 1 or beta 3 cRNAs results in the expression of functional Na-K pumps that share similar low ouabain sensitivity but differ in their K+ half activation constant (K1/2). Similar results were obtained with Xenopus alpha 1 and beta 1 or beta 3 subunits and with Bufo/Xenopus heterodimers. We conclude that some specific sequence of the beta subunit can influence the activation of the Na,K pump by extracellular K+ ions.
我们最近克隆了海蟾蜍（Bufo marinus）钠钾ATP酶的α1、β1和β3亚基。为了研究β1和β3之间可能存在的功能差异，我们对非洲爪蟾（Xenopus laevis）卵母细胞中表达的钠钾泵K⁺激活情况进行了研究。钠钾泵活性通过电压钳制卵母细胞中K⁺诱导电流来测定。我们可以利用蟾蜍α亚基赋予的对哇巴因的相对抗性，在抑制对哇巴因敏感的内源性非洲爪蟾钠钾泵后，专门研究外源性表达的钠钾泵。将蟾蜍α1亚基的cRNA与β1或β3的cRNA共注射，会导致功能性钠钾泵的表达，这些泵具有相似的低哇巴因敏感性，但K⁺半激活常数（K1/2）不同。用非洲爪蟾的α1和β1或β3亚基以及蟾蜍/非洲爪蟾异源二聚体也得到了类似的结果。我们得出结论，β亚基的某些特定序列可影响细胞外K⁺离子对钠钾泵的激活。
