Effects of Na(+) on the predominant K(+) channel in the tonoplast of Chara: decrease of conductance by blocks in 100 nanosecond range and induction of oligo- or poly-subconductance gating modes.
We present three mechanisms by which Na(+) inhibits the open channel currents of the predominant K(+) channel in the tonoplast of Chara corallina: (i) Fast block, i.e., short (100 ns range) interruptions of the open channel current which are determined by open channel noise analysis, (ii): Oligo-subconductance mode, i.e., a gating mode which occurs preferentially in the presence of Na(+); this mode comprises a discrete number (here 3) of open states with smaller conductances than normal, and (iii): Polysubconductance mode, i.e., a gating mode with a nondiscrete, large number (>30) of states with smaller conductances than the main open channel conductance. This novel mode has also been observed only in the presence of Na(+).
Weise
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R
Abteilung Biophysik der Pflanze, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany.
Gradmann
D
D
D004553:Electric Conductivity; D056890:Eukaryota / Q000187:drug effects / Q000378:metabolism*; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*
D015221:Potassium Channels; D012964:Sodium