TRANSPORT OF ZN2+ CO2+ AND NI2+ INTO YEAST CELLS

Ni2+, Co2+, Zn2+ can be taken up into a non-exchangeable pool by yeast cells, by a system that also transports Mg2+ and Mn2+. The affinity series is Mg2+, Co2+, Zn2+ > Mn2+ > Ni2+ > Ca2+ > Sr2+. The uptake is small in starved cells, but is enhanced in the presence of glucose. It is remarkably stimulated (5-20 fold) if cells are pretreated with phosphate and glucose. The uptakes are the same under aerobic or anaerobic conditions suggesting that fermentative reactions can supply the energy for transport. Uptake is reduced at low pH (below 5.0), but a H+ exchange system is not involved. Instead, 2 K+ (or 2 Na+ in Na+-loaded cells) are secreted for each divalent cation absorbed. © 1968.