The gamma subunit is a specific component of the Na,K-ATPase and modulates its transport function
The gamma subunit is a specific component of the Na,K-ATPase and modulates its transport function
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DOI：
10.1093/emboj/16.14.4250
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发表时间：
1997-07-16
期刊：
影响因子：
11.4
通讯作者：
Geering, K
中科院分区：
文献类型：
--
作者：
Beguin, P;Wang, XY;Geering, K
与离子泵或离子通道相关的小疏水肽的作用仍然知之甚少。利用非洲爪蟾卵母细胞作为表达系统，我们已经表征了与Na，K-ATP酶共纯化的γ肽的结构和功能特性。免疫放射性标记的抗原表位标记的γ亚基在完整的卵母细胞和蛋白酶保护试验表明，γ肽是一种I型膜蛋白缺乏信号序列和暴露的N-末端的胞外侧，去表达的大鼠或非洲爪蟾γ亚基与卵母细胞中的各种蛋白质，揭示了它只与Na，K-ATP酶的同工酶特异性。γ肽不影响功能性Na，K-ATP酶α-β复合物的形成和细胞表面表达。另一方面，γ肽本身需要与Na，K-ATP酶结合，以便在卵母细胞中稳定表达并有效转运至质膜，γ亚基不与单个α或β亚基结合，而仅与组装的α或β亚基相互作用，最后，电生理学测量表明，γ肽调节Na，K泵的K+激活。这些数据首次证明了膜拓扑结构、缔合的特异性和Na，K-ATP酶γ亚基的潜在功能作用。
The role of small, hydrophobic peptides that are associated with ion pumps or channels is still poorly understood. By using the Xenopus oocyte as an expression system, we have characterized the structural and functional properties of the gamma peptide which co-purifies with Na,K-ATPase. Immuno-radiolabeling of epitope-tagged gamma subunits in intact oocytes and protease protection assays show that the gamma peptide is a type I membrane protein lacking a signal sequence and exposing the N-terminus to the extracytoplasmic side, Go-expression of the rat or Xenopus gamma subunit with various proteins in the oocyte reveals that it specifically associates only with isozymes of Na,K-ATPase. The gamma peptide does not influence the formation and cell surface expression of functional Na,K-ATPase alpha-beta complexes, On the other hand, the gamma peptide itself needs association with Na,K-ATPase in order to be stably expressed in the oocyte and to be transported efficiently to the plasma membrane, gamma subunits do not associate with individual alpha or beta subunits but only interact with assembled, transport-competent alpha-beta complexes, Finally, electrophysiological measurements indicate that the gamma peptide modulates the K+ activation of Na,K pumps, These data document for the first time the membrane topology, the specificity of association and a potential functional role for the gamma subunit of Na,K-ATPase.