Vanadate uptake in Neurospora crassa occurs via phosphate transport system II

Abstract

Vanadate, a potent inhibitor of plasma membrane ATPases, is taken up by N. crassa only when cells are growing in alkaline medium and starving for phosphate. The appearance of a vanadate uptake system (K(m) = 8.2 μM; V(max) = 0.15 mmol/min per liter of cell water) occurs under the same conditions required for derepression of a high-affinity phosphate transport system. Phosphate is a competitive inhibitor of vanadate uptake, and vanadate is a competitive inhibitor of phosphate uptake. Furthermore mutant strains which are either partially constitutive or non-derepressible for the high-affinity phosphate transport system are also partially constitutive or non-derepressible for vanadate uptake. These data indicate that vanadate enters the cell via phosphate transport system II.