Ion channels in the thylakoid membrane (a patch-clamp study)

Abstract

Thylakoid membranes were fused with azolectin liposomes and enlarged to giant thylakoid/liposome vesicles with diameters between 20 μm and 50 μm by a modified dehydration/rehydration procedure. Ion transport across the membrane of these giant thylakoid/liposome vesicles was investigated by the patch-clamp technique. Single-channel currents were observed and four different specific ion conductances could be distinguished. Our results indicate that these conductances can be attributed to three types of ion channel: a putative potassium channel with a conductance of 110 pS (in 100 mM KCl) a chloride channel with a conductance of 220 pS (in 100 mM KCl) and a moderate selectivity of about 4:1 for anions over cations. The third type of putative ion channel we observed was permeable to Mg 2+ and Ca 2+ ions with conductances of 20 pS for Ca 2+ and 35 pS for Mg 2+, respectively.