Active transport of magnesium across the yeast cell membrane

Abstract

Magnesium ions can be actively transported in large amounts across the yeast-cell membrane by the physiological carrier of K+ ions. This occurs only when the Mg++ ion is the only inorganic cation present in the external fluid in appreciable concentration. The uptake of magnesium in this way from 0.2 [image] concentration is 50% inhibited by 0.58 m[image] K+ ion and is inhibited by other inorganic cations in varying degrees. The strongest inhibitor of the uptake of magnesium is H ion; below pH 5.5 magnesium is not taken up by the same mechanism in appreciable amounts. The uptake of Mg++ ions is inhibited by anoxia or by cyanide (2 m[image]) and azide (2 m[image]). When present as the acetate, propionate, butyrate or valerate it is not inhibited by 2,4-dinitrophenol (2 m[image]) but it is inhibited by this when present as the chloride or sulfate. Even when large amounts of Mg++ ions are taken up, practically none come out on reimmersion in water or even in 0.1 [image] KC1 during fermentation.