Copper accumulation in the cell-wall-deficient slime variant of Neurospora crassa. Comparison with a wild-type strain

The copper-uptake process in the cell-wall-deficient slime variant of the fungus Neurospora crassa was compared with that in a wild-type strain. In both organisms investigated most of the copper is taken up from the culture medium during the exponential growth period. The wild-type strain, however, accumulates much more copper than does the slime variant. The influence of the copper concentration in the culture medium on the amounts of copper accumulated intracellularly suggests separate ways of copper import used by the two morphologically different N. crassa strains. Copper analyses of three different cytosolic fractions as a function of growth time or exogenous copper concentration indicate both strains to share a very similar copper metabolism. All the data presented are consistent with a detoxification function of the low-Mr copper-binding fraction of N. crassa. Both copper-metallothionein and oxidized glutathione (GSSG) are co-eluted with this fraction. The possible involvement of glutathione in metallothionein biosynthesis is discussed.