Mitochondria of Isolated Plant Cells (Acer pseudoplatanus L.): II. Copper Deficiency Effects on Cytochrome C Oxidase and Oxygen Uptake.

The effects of copper deficiency on cell culture growth, cell respiration, mitochondrial oxidative properties, and electron transport chain have been studied with suspension-cultured sycamore cells (Acer pseudoplatanus L.). Within the range of the copper concentration studied (0.1-25 mug/1 of culture medium), the mean rate of cell division is independent of copper concentration. An initial copper concentration lower than 2 mug/1 limited the maximum density of population reached at the stationary phase of growth.On a protein basis, the uncoupled O(2) uptake rates were about the same for normal and copper-deficient cells. In contrast, the half-maximal inhibition of O(2) uptake rate was obtained at greater KCN concentration in the normal cells (20 muM) compared to copper-deficient cells (2 muM). Similar results were obtained with the normal and copper-deficient sycamore cell mitochondria.In the copper-deficient mitochondria, the concentration of the cytochrome aa(3) was less than 0.02 nmol/mg mitochondrial protein or 1/20 of the normal rate. The b- and c-type cytochrome content was invariant with copper depletion. It appeared that cytochrome aa(3) is present in large excess in normal cells. This work also indicated that cytochrome c is a very mobile molecule.