包含胃H⁺-K⁺-ATP酶α亚基Q905-V930的Na⁺-K⁺-ATP酶α亚基优先与H⁺-K⁺-ATP酶β亚基组装。
Na+-K+-ATPase alpha-subunit containing Q905-V930 of gastric H+-K+-ATPase alpha preferentially assembles with H+-K+-ATPase beta.
作者信息
Wang S G, Eakle K A, Levenson R, Farley R A
机构信息
Department of Physiology and Biophysics, University of Southern California, Los Angeles 90033, USA.
出版信息
Am J Physiol. 1997 Mar;272(3 Pt 1):C923-30. doi: 10.1152/ajpcell.1997.272.3.C923.
Amino acids N886-A911 of the rat Na+-K+-ATPase alpha3-subunit were replaced by the corresponding region (Q905-V930) of the rat gastric H+-K+-ATPase alpha-subunit. The chimera (NGH26) was expressed in yeast with the rat Na+-K+ -ATPase beta1-subunit (rbeta1), the rat H+-K+-ATPase beta-subunit (HKbeta), the chimeric beta-subunit NHbeta1 (containing the carboxy-terminal ectodomain of HKbeta), or the chimeric beta-subunit HNbeta1 (containing the carboxy-terminal ectodomain of rbeta1). Increased resistance to trypsin digestion indicated that NGH26 preferentially assembled with HKbeta and NHbeta1 rather than with rbeta1 or HNbeta1. Ouabain binding also indicated that more functional complexes were assembled when NGH26 was expressed with HKbeta or NHbeta1. These results suggest that the sequence Q905-V930 interacts with the HKbeta-subunit on the extracellular side of the cell membrane. The NGH26 + HKbeta complex is less stable than alpha3 + HKbeta when heated and also has a lower binding affinity for ouabain [dissociation constant (Kd) = 63 nM] compared with alpha3 + rbeta1 or alpha3 + HKbeta (K(d) = 5-10 nM). In contrast, the NGH26+NHbeta1 complex is thermally as stable as alpha3 + rbeta1 complexes, and its ouabain binding affinity (K(d) = 10 nM) is the same as the wild type. These results indicate that the amino acids Q905-V930 of the rat gastric H+-K+-ATPase alpha-subunit preferentially associate with the extracellular domain of H+-K+-ATPase beta-subunit to form functional pump complexes and that the cytoplasmic and/or transmembrane region of the beta-subunit influences the stability of the alpha beta complexes.
大鼠Na⁺-K⁺-ATP酶α3亚基的氨基酸N886 - A911被大鼠胃H⁺-K⁺-ATP酶α亚基的相应区域（Q905 - V930）取代。该嵌合体（NGH26）与大鼠Na⁺-K⁺-ATP酶β1亚基（rbeta1）、大鼠H⁺-K⁺-ATP酶β亚基（HKbeta）、嵌合β亚基NHbeta1（包含HKbeta的羧基末端胞外结构域）或嵌合β亚基HNbeta1（包含rbeta1的羧基末端胞外结构域）在酵母中表达。对胰蛋白酶消化的抗性增加表明，NGH26优先与HKbeta和NHbeta1组装，而不是与rbeta1或HNbeta1组装。哇巴因结合也表明，当NGH26与HKbeta或NHbeta1一起表达时，会组装更多功能性复合物。这些结果表明，序列Q905 - V930在细胞膜胞外侧与HKbeta亚基相互作用。与α3 + rbeta1或α3 + HKbeta（Kd = 5 - 10 nM）相比，NGH26 + HKbeta复合物在加热时不如α3 + HKbeta稳定，并且对哇巴因的结合亲和力也较低[解离常数（Kd）= 63 nM]。相反，NGH26 + NHbeta1复合物在热稳定性上与α3 + rbeta1复合物相同，其哇巴因结合亲和力（Kd = 10 nM）与野生型相同。这些结果表明，大鼠胃H⁺-K⁺-ATP酶α亚基的氨基酸Q905 - V930优先与H⁺-K⁺-ATP酶β亚基的胞外结构域结合形成功能性泵复合物，并且β亚基的胞质和/或跨膜区域影响αβ复合物的稳定性。
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