Open AccessDepolarization-Activated K+ Channel in Chara Droplets
Author(s) -
Igor Pottosin,
Pavle R. Anđjus
Publication year - 1994
Publication title -
plant physiology
Language(s) - Slovenian
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.106.1.313
Subject(s) - depolarization , conductance , tetraethylammonium , chemistry , chara , hyperpolarization (physics) , potassium , selectivity , chloride channel , potassium channel , tetraethylammonium chloride , membrane potential , repolarization , gating , biophysics , analytical chemistry (journal) , electrophysiology , stereochemistry , biochemistry , chromatography , botany , physics , biology , organic chemistry , condensed matter physics , neuroscience , nuclear magnetic resonance spectroscopy , catalysis
A novel potassium channel was characterized in the droplet membrane of Chara gymnophylla. This channel has a conductance of about 90 pS (in symmetrical 0.15 M KCl), which is lower compared to the 170-pS K+ channel predominant in this preparation. In contrast to the large conductance K+ channel, the novel channel opened with a delay at depolarization and closed at hyperpolarization and did not require cytosolic Ca2+ for its opening. It also showed comparatively weak selectivity for K+ over other monovalent cations, although its cation to anion selectivity was high. Externally or internally applied Cs+ blocked the channel in a voltage-dependent manner, similarly to the 170-pS channel. The sensitivity of the 90-pS channel to external tetraethylammonium chloride (half-blocking concentration approximately 1.5 mM) was 20-fold higher compared to the large conductance channel. With respect to its voltage-gating kinetics, the 90-pS channel was identified as a "slow delayed rectifier."