The mechanism of uptake of cobalt ions by Neurospora crassa

Abstract

Uptake of Co²⁺ 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 Co²⁺ uptake. Transport of Co²⁺ occurs at a rate of 40μg/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 Co²⁺. The overall uptake of Co²⁺ exhibits a high K_m value and hence the concentration mechanism is one of low `affinity' for the metal. The uptake of Co²⁺ varies linearly with pH in the range pH3 to pH6. Mg²⁺ inhibits both surface binding and transport of Co²⁺. It is suggested that the system that transports Mg²⁺ is also involved in Co²⁺ uptake by N. crassa.