Cytoplasmic magnesium regulates the fast activating vacuolar cation channel

Abstract

Abstract physiological tonoplast potentials (Hedrich and Neher,1987; Allen and Sanders, 1996; Tikhonova et al ., 1997).Fast activating vacuolar (FV) channels, which are per-Due to its selectivity for monovalent cations (Bru¨ggemannmeable for small monovalent cations, dominate the ion et al ., 1999) the FV channel could mediate a rather highconductance of the vacuolar membrane at physio-K+permeability of the tonoplast clamping the tonoplastlogical Ca2+ concentrations. Here the effect of Mg2+potential close to the equilibrium potential for K+on FV channels was studied. Patch-clamp measure-(Tikhonova et al ., 1997). Cytosolic free Ca2+concentra-ments were performed on whole barley (Hordeum vul-tions in the micromolar range decrease the open probabil-gare) mesophyll vacuoles and on excised tonoplastity of FV channels (Hedrich and Neher, 1987; Allen andpatches. Free Mg2+ concentrations in the millimolarSanders, 1996). However, with K dvalues of 6 mMinrange inhibited FV channels from the cytosolic and thebarley mesophyll cells (Tikhonova