Evidence for coenzyme Q function in transplasma membrane electron transport.

Transplasma membrane electron transport activity has been associated with stimulation of cell growth. Coenzyme Q is present in plasma membranes and because of its lipid solubility would be a logical carrier to transport electrons across the plasma membrane. Extraction of coenzyme Q from isolated rat liver plasma membranes decreases the NADH ferricyanide reductase and added coenzyme Q10 restores the activity. Piericidin and other analogs of coenzyme Q inhibit transplasma membrane electron transport as measured by ferricyanide reduction by intact cells and NADH ferricyanide reduction by isolated plasma membranes. The inhibition by the analogs is reversed by added coenzyme Q10. Thus, coenzyme Q in plasma membrane may act as a transmembrane electron carrier for the redox system which has been shown to control cell growth.