Kürz L, Wagner S, George A L, Rüdel R
Abteilung für Allgemeine Physiologie, Universität Ulm, D-89069 Ulm, Germany.
Pflugers Arch. 1997 Jan;433(3):357-63. doi: 10.1007/s004240050288.
The sensitivity of the human skeletal muscle Cl- channel, hClC-1, towards various sulfhydryl-reactive agents was tested with the channel expressed in Xenopus oocytes and in human embryonic kidney cells. External but not internal Zn2+, at 1 mM, substantially reduced the current without affecting activation parameters. External Cd2+ and Hg2+ as well as organic mercurial compounds reduced the Cl- currents to a similar degree. With the mutant channel hClC-1 D136G, presumed to have a defective voltage sensor, external Zn2+ also reduced the current without effect on the altered gating. These findings suggest that hClC-1 contains cysteine residues near the extracellular face that may directly influence ion conduction. Since Zn2+ can also bind to histidine side chains, we tested the effect of compounds with either more cysteine- or more histidine-specificity. The results confirm the involvement of cysteine(s) in the observed effects but do not exclude the involvement of histidine(s).
利用非洲爪蟾卵母细胞和人胚肾细胞中表达的氯离子通道，测试了人类骨骼肌氯离子通道hClC-1对各种巯基反应性试剂的敏感性。外部（而非内部）1 mM的Zn2+能显著降低电流，但不影响激活参数。外部的Cd2+、Hg2+以及有机汞化合物能使氯离子电流降低到相似程度。对于推测电压感受器有缺陷的突变通道hClC-1 D136G，外部Zn2+同样能降低电流，且不影响改变后的门控。这些发现表明，hClC-1在细胞外表面附近含有半胱氨酸残基，可能直接影响离子传导。由于Zn2+也能与组氨酸侧链结合，我们测试了对半胱氨酸或组氨酸特异性更强的化合物的作用。结果证实了半胱氨酸参与了观察到的效应，但不排除组氨酸的参与。
