Modification of voltage-dependent gating of potassium channels by free form of tryptophan side chain.
Indole constitutes a major component of the side chain of the amino acid tryptophan. Application of indole slows activation of voltage-dependent potassium channels and reduces steady-state conductance in a voltage- and concentration-dependent manner. The steep concentration dependence indicates that multiple indole molecules may interact with the channel. Indole does not noticeably change the unitary conductance or the mean open duration, however, it accelerates off-gating currents without altering on-gating currents. These properties of the modification of channel gating induced by indole are consistent with a model in which indole binds independently to every subunit of the channel complex to prevent the final concerted transition to the open state. We suggest that exogenously applied indole and side-chains of the tryptophan residues of the channel protein involved in activation may compete for the same effector position and that indole might be useful as a probe to study functional roles of tryptophan residues.
Avdonin
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Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242, USA.
Hoshi
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D000818:Animals; D004594:Electrophysiology; D007211:Indoles / Q000737:chemistry* / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D007700:Kinetics; D008954:Models, Biological; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011804:Quinolines / Q000737:chemistry / Q000494:pharmacology; D051637:Shaker Superfamily of Potassium Channels; D013329:Structure-Activity Relationship; D014364:Tryptophan / Q000737:chemistry* / Q000494:pharmacology*; D014981:Xenopus
D007211:Indoles; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011804:Quinolines; D051637:Shaker Superfamily of Potassium Channels; C030374:indole; D014364:Tryptophan; C037219:quinoline