[Reducing centers on the surface of Escherichia coli bacteria and their role in copper-induced plasma membrane permeability].

The reducing properties of Escherichia coli and their role in the induction of nonselective cationic permeability of plasma membrane by the action of Cu2+ ions were studied. The ability of cells to reduce exogenous dithiopyridine was shown to be maximal in freshly collected culture and to decrease upon starvation or exhaustion of bacteria by dinitrophenol, in the presence of other oxidants of cell thiols in the medium, and after the disturbance of the barrier properties of membrane by tetrachloracetic acid or butanol. The alkylation of cell thiols accessible for N-ethyl maleimide completely disrupted the reducing activity of bacteria. These data are consistent with the conception that the reduction of dithiopyridine and Cu2+ ions by bacteria occurs on the thiol-containing centers of the cell surface, which are continuously reduced by the transfer of cell reducing equivalents from the inner to the outer surface of plasma membrane. The analysis of data on the effect of external oxidizing and reducing agents on the copper-induced plasmolysis of bacteria showed that the induction of membrane permeability by the action of copper can occur upon interaction with critical targets on the surface of Cu+ ions formed in the periplasmic space in the reaction of Cu2+ ions with reducing centers.