Probing the major skeletal muscle chloride channel with Zn2+ and other sulfhydryl-reactive compounds.
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).
Kürz
L
L
Abteilung für Allgemeine Physiologie, Universität Ulm, D-89069 Ulm, Germany.
Wagner
S
S
George
A L
AL
Rüdel
R
R
D018118:Chloride Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007668:Kidney / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects*; D009865:Oocytes; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D015032:Zinc / Q000494:pharmacology*
D018118:Chloride Channels; D013438:Sulfhydryl Compounds; D015032:Zinc