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Potassium ion channels in the plasmalemma
Author(s) -
Bentrup FriedrichWilhelm
Publication year - 1990
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1990.tb00048.x
Subject(s) - biophysics , conductance , membrane potential , chemistry , potassium channel , gating , potassium , ion channel , patch clamp , osmolyte , population , cytosol , ion transporter , inward rectifier potassium ion channel , reversal potential , membrane , biochemistry , biology , receptor , demography , organic chemistry , sociology , enzyme , mathematics , combinatorics
The potassium ion is an indispensible cytosolic component of living cells and a key osmolyte of plant cells, crossing the plasmalemma to drive physiological processes like cell growth and motor cell activity. K + transport across the plasmalemma may be passive through channels, driven by the electrochemical gradient, K + equilibrium potential (E K ) – membrane potential (V m ), or secondary active by coupling through a carrier to the inward driving force of H + or Na + . Known K + channels are permeable to monovalent cations, a permeability order being K + > Rb + > NH 4 + > Na + ≥ Li + > Cs + . The macroscopic K + currents across a cell or protoplast surface commonly show rectification, i.e. a V m ‐dependent conductance which in turn, may be controlled by the cytosolic activity of Ca 2+ , of K + , of H + , or by the K + driving force. Analysis by the patch clamp technique reveals that plant K + channels are similar to animal channels in their single channel conductance (4 to 100 pS), but different in that a given channel population slowly activates and may not inactivate at all. Single‐channel kinetics reveal a broad range of open times (ms to s) and closed times (up to 100 s). Further progress in elucidating plant K + channels will critically depend on molecular cloning, and the availability of channel‐specific (phyto)toxins.