MAIN MECHANISMS OF ION TRANSPORT AND REGULATION OF ION CONCENTRATION IN THE YEAST CYTOPLASM

Abstract

The key point of transport energization across the plasma and vacuolar membrane of fungi is the generation of the electrochemical gradient of protons by H+-ATPases of both membranes. The gradient of K+ is used to increase the energy capacity of the H+ gradient. The regulation of ion concentrations in the yeast cytosol is based on the activity of transporters of plasmalemma and tonoplast. This chapter discusses the transport of Mn2+ or other divalent cations (Me2+). Mn2+ uptake by yeasts is an energy-dependent process. It is driven by the H+ gradient both in the presence and in the absence of glucose: protonophores inhibit the accumulation of Mn2+ and Co2+. The dissipation of the K+ gradient by different reagents decreases the Mn2+ uptake. Candicydin brings about a rapid and complete loss of the intracellular K+ and inhibits Mn2+ uptake. The inhibition of Mn2+ uptake by reagents collapsing the K+ and H+ gradients point to the participation of these gradients in the energization of the Mn2+ uptake. The chapter presents results that support the electrogenic efflux of K+.