A PUTATIVE K+-SELECTIVE CHANNEL IN THE PLASMA-MEMBRANE OF YEAST THAT IS BLOCKED BY MICROMOLAR CONCENTRATIONS OF EXTERNAL DIVALENT-CATIONS AND IS INSENSITIVE TO TETRAETHYLAMMONIUM

At pH 7, addition of glucose to an anaerobic suspension of non-metabolizing yeast cells causes a transient net efflux of K+ from the cells and a concomitant transient hyperpolarization of the plasma membrane (Van de Mortel, J.B.J. et al. (1988) Biochim. Biophys. Acta 936, 421-428). Both phenomena are effectively suppressed in the presence of low concentrations of polyvalent cations. The concentrations of Mn2+, Ca2+, Ba2+, Mg2+, Sr2+ and La3+ required for half-maximal suppression of the transient hyperpolarization are 10, 17, 20, 38, 47 and 5 μM, respectively. Subsequent addition of EDTA 90 s after that of Ca2+ immediately restores both K+ efflux and cellular uptake of the fluorescent membrane potential probe 2-(dimethylaminostyryl)-1-ethylpyridinium (DMP). This suggests that an interaction of polyvalent cations with an external binding site blocks the putative K+-selective channel. Opening of this channel is not blocked by 20 mM tetraethylammonium nor by 100 μM 3,4-diaminopyridine. It is argued that this glucose-induced K+-conductive pathway is not identical to the voltage-gated K+ channels identified until now in patch-clamp studies of the yeast plasma membrane. © 1990.