单价阳离子与从猪肾中纯化的钠钾依赖型ATP酶的结合。III. 由形成对ADP不敏感而非对ADP敏感的磷酸酶所诱导的单价阳离子亲和力的显著变化。

Binding of monovalent cations to Na+,K+-dependent ATPase purified from porcine kidney. III. Marked changes in affinities for monovalent cations induced by formation of an ADP-insensitive but no an ADP-Sensitive phosphoenzyme.

作者信息

Yamaguchi M, Tonomura Y

出版信息

J Biochem. 1980 Nov;88(5):1387-97. doi: 10.1093/oxfordjournals.jbchem.a133107.

DOI:10.1093/oxfordjournals.jbchem.a133107

Abstract

We measured the amounts of Rb+ ions (a K+ congener) as well as Na+ and K+ ions bound to the ATPase during the ATPase reaction at pH 7.5 and 0 degrees C. The affinity of the Na+-binding sites for three Na+ ions decreased markedly but that of the K+-binding sites for two K+ or Rb+ ions increased markedly upon formation of an ADP-insensitive phosphorylated intermediate. Furthermore, the present experiment did not give any indication of a change in the Hill coefficient of 2, and showed an increase in the affinity of the K+-binding sites for Rb+ ions of about 28 times upon the formation of an ADP-insensitive EP. The enzyme state with a high affinity for Rb+ was maintained after the disappearance of EP. When the ATPase was treated with N-ethylmaleimide (NEM), almost all the EP formed was ADP-sensitive. The formation of an ADP-sensitive EP with the NEM-treated enzyme induced no change in the affinities of the ATPase for Na+ and Rb+ ions.

摘要

我们在pH 7.5和0℃的ATP酶反应过程中，测量了与ATP酶结合的Rb⁺离子（一种K⁺同系物）以及Na⁺和K⁺离子的量。在形成对ADP不敏感的磷酸化中间体时，三个Na⁺离子的Na⁺结合位点的亲和力显著降低，但两个K⁺或Rb⁺离子的K⁺结合位点的亲和力显著增加。此外，本实验未显示Hill系数为2有任何变化，并且显示在形成对ADP不敏感的EP时，K⁺结合位点对Rb⁺离子的亲和力增加了约28倍。在EP消失后，对Rb⁺具有高亲和力的酶状态得以维持。当ATP酶用N - 乙基马来酰亚胺（NEM）处理时，几乎所有形成的EP对ADP敏感。用NEM处理的酶形成对ADP敏感的EP不会引起ATP酶对Na⁺和Rb⁺离子亲和力的变化。