Mechanism of action of the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline on Mycoplasma gallisepticum.

Evidence was found that the inhibitory action of Cu(DMP)2NO3, the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline (DMP), on Mycoplasma gallisepticum is a consequence of the ultimate toxicity of copper, and not that of the ligand, DMP. From uptake studies with radiolabeled 67Cu and [14C]DMP, we concluded that significantly more copper than DMP is bound to the mycoplasmal cell. It appeared that dissociation of Cu(DMP)2+ occurred shortly after interaction with the cell membrane. Copper was transported across the cytoplasmic membrane. A strong dependence of copper uptake on the incubation medium was observed in the absence of DMP. The main function of the ligand DMP appeared to be as a vehicle for the transport of copper from nontoxic copper-medium complexes to membrane-buried cellular ligands.