人类非胃H⁺-K⁺-ATP酶：与不同β亚基组装的ATP1al1的转运特性。

Human nongastric H+-K+-ATPase: transport properties of ATP1al1 assembled with different beta-subunits.

作者信息

Crambert Gilles, Horisberger Jean-Daniel, Modyanov Nikolai N, Geering Käthi

机构信息

Institute Of Pharmacology And Toxicology of The University, CH-1005 Lausanne, Switzerland.

出版信息

Am J Physiol Cell Physiol. 2002 Jul;283(1):C305-14. doi: 10.1152/ajpcell.00590.2001.

DOI:10.1152/ajpcell.00590.2001

PMID:12055100

Abstract

To investigate whether nongastric H+-K+-ATPases transport Na+ in exchange for K+ and whether different beta-isoforms influence their transport properties, we compared the functional properties of the catalytic subunit of human nongastric H+-K+-ATPase, ATP1al1 (AL1), and of the Na+-K+-ATPase alpha1-subunit (alpha1) expressed in Xenopus oocytes, with different beta-subunits. Our results show that betaHK and beta1-NK can produce functional AL1/beta complexes at the oocyte cell surface that, in contrast to alpha1/beta1 NK and alpha1/betaHK complexes, exhibit a similar apparent K+ affinity. Similar to Na+-K+-ATPase, AL1/beta complexes are able to decrease intracellular Na+ concentrations in Na+-loaded oocytes, and their K+ transport depends on intra- and extracellular Na+ concentrations. Finally, controlled trypsinolysis reveals that beta-isoforms influence the protease sensitivity of AL1 and alpha1 and that AL1/beta complexes, similar to the Na+-K+-ATPase, can undergo distinct K+-Na+- and ouabain-dependent conformational changes. These results provide new evidence that the human nongastric H+-K+-ATPase interacts with and transports Na+ in exchange for K+ and that beta-isoforms have a distinct effect on the overall structural integrity of AL1 but influence its transport properties less than those of the Na+-K+-ATPase alpha-subunit.

摘要

为了研究非胃H⁺-K⁺-ATP酶是否能转运Na⁺以交换K⁺，以及不同的β亚型是否会影响其转运特性，我们比较了在非洲爪蟾卵母细胞中表达的人非胃H⁺-K⁺-ATP酶催化亚基ATP1al1（AL1）和Na⁺-K⁺-ATP酶α1亚基（α1）与不同β亚基的功能特性。我们的结果表明，βHK和β1-NK能在卵母细胞表面产生功能性的AL1/β复合物，与α1/β1 NK和α1/βHK复合物不同，它们表现出相似的表观K⁺亲和力。与Na⁺-K⁺-ATP酶相似，AL1/β复合物能够降低Na⁺负载的卵母细胞中的细胞内Na⁺浓度，并且它们的K⁺转运取决于细胞内和细胞外的Na⁺浓度。最后，可控的胰蛋白酶消化显示，β亚型会影响AL1和α1的蛋白酶敏感性，并且AL1/β复合物与Na⁺-K⁺-ATP酶相似，可经历不同的K⁺-Na⁺和哇巴因依赖性构象变化。这些结果提供了新的证据，表明人非胃H⁺-K⁺-ATP酶能与Na⁺相互作用并转运Na⁺以交换K⁺，并且β亚型对AL1的整体结构完整性有明显影响，但对其转运特性的影响小于Na⁺-K⁺-ATP酶α亚基。