Blockade of the K+ Channel of Chara-Contraria by Cs+ and Tetraethylammonium Resembles That of K+ Channels in Animal- Cells

ZANELLO LP; BARRANTES FJ

PLANT SCIENCE

ELSEVIER IRELAND LTD

Lugar: Dublin; Año: 1992 vol. 86 p. 49 - 58

0168-9452

Cell-sized vesicles devoid of cell wall (?droplets?) were obtained from the giant internodal cells of the algae Chara contraria and studied by means of the patch-clamp technique. A K+ channel appears to be the most frequent type present in this membrane. It exhibits a high conductance (100 pS in symmetric 100 mM KC1), voltage-dependent behavior, Ca2+ sensitivity and marked selectivity for K+ over Na+. Here we present for the first time, at the level of single-channel recording in a plant ionic channel, the permeability blockade exerted by two typical K+ channel inhibitors, the ions Cs+ and tetraethylammonium (TEA+). Blockade by Cs+ was found to be concentration- and voltage-dependent. TEA+ affected both inward and outward K+ currents when applied to either side of the membrane. The effects of similar to those exerted by these ions on certain types of K+ channels in animal cells. In addition, the results are indicative of the existence of binding sites for TEA+ near the two ends of the channel vestibules and suggest structural asymmetry between these two domains.