Asymmetry of the red cell anion exchange system. Different mechanisms of reversible inhibition by N-(4-azido-2-nitrophenyl)-2- aminoethylsulfonate (NAP-taurine) at the inside and outside of the membrane
Asymmetry of the red cell anion exchange system. Different mechanisms of reversible inhibition by N-(4-azido-2-nitrophenyl)-2- aminoethylsulfonate (NAP-taurine) at the inside and outside of the membrane
复制标题
红细胞阴离子交换系统的不对称性。
DOI：
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
A. Rothstein
中科院分区：
文献类型：
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作者：
P. A. Knauf;S. Ship;W. Breuer;L. McCulloch;A. Rothstein
在黑暗中，光亲和试剂，N-（4-叠氮基-2-硝基苯基）-2-氨基乙基磺酸盐（NAP-牛磺酸），作为一个可逆的抑制剂红细胞阴离子交换时，它是存在于细胞内或在外部解决方案。然而，对抑制动力学的详细分析揭示了膜两侧对探针的响应存在实质性差异。在细胞内部，NAP-牛磺酸是一种相对低亲和力的氯离子交换抑制剂（Ki = 370 μ M）。氯化物对NAP-牛磺酸抑制的影响和NAP-牛磺酸作为底物对系统的亲和力与内部NAP-牛磺酸与氯化物竞争阴离子交换系统的底物位点的概念一致。另一方面，外部NAP-牛磺酸是一种更有效的氯离子交换抑制剂（Ki = 20 μ M）。它的作用在一个网站的亲和力相当低的氯离子比基板网站，可能是改性剂网站，在该网站的卤素阴离子据报道，造成非竞争性抑制氯离子转运。因此，NAP-牛磺酸似乎优先与转运系统的底物或修饰位点相互作用，这取决于它存在的膜的一侧。有人建议，改性剂的网站是访问NAP-牛磺酸只从外面，而运输网站可以从任何一方。
In the dark, the photoaffinity reagent, N-(4-azido-2-nitrophenyl)-2- aminoethylsulfonate (NAP-taurine), acts as a reversible inhibitor of red cell anion exchange when it is present either within the cell or in the external solution. A detailed analysis of the inhibition kinetics, however, reveals substantial differences in the responses to the probe at the two sides of the membrane. On the inside of the cell, NAP- taurine is a relatively low affinity inhibitor of chloride exchange (Ki = 370 microM). Both the effects of chloride on NAP-taurine inhibition and the affinity of NAP-taurine for the system as a substrate are consistent with the concept that internal NAP-taurine competes with chloride for the substrate site of the anion exchange system. External NAP-taurine, on the other hand, is a far more potent inhibitor of chloride exchange (Ki = 20 microM). It acts at a site of considerably lower affinity for chloride than the substrate site, probably the modifier site, at which halide anions are reported to cause a noncompetitive inhibition of chloride transport. NAP-taurine therefore seems to interact preferentially with either the substrate or modifier site of the transport system, depending on the side of the membrane at which it is present. It is suggested that the modifier site is accessible to NAP-taurine only from the outside whereas the transport site may be accessible from either side.