The mechanism of uptake of cobalt ions by Neurospora crassa

Uptake of Co(2+) by 3-day-old mycelia of Neurospora crassa involves cell-surface binding as well as transport into the intracellular space. The surface binding is rapid and accounts for 30-40% of the total Co(2+) uptake. Transport of Co(2+) occurs at a rate of 40mug/h per 100mg dry wt. Surface binding and overall uptake show different temperature dependence. Metabolic inhibitors such as azide, dinitrophenol and fluoride depress transport of Co(2+). The overall uptake of Co(2+) exhibits a high K(m) value and hence the concentration mechanism is one of low ;affinity' for the metal. The uptake of Co(2+) varies linearly with pH in the range pH3 to pH6. Mg(2+) inhibits both surface binding and transport of Co(2+). It is suggested that the system that transports Mg(2+) is also involved in Co(2+) uptake by N. crassa.