Role of metal ion free valinomycin-carbonyl cyanide m-chlorophenylhydrazone complex in the enhancement of the rates of gramicidin facilitated net H +, Li + and Na + transport across phospholipid vesicular membrane

Abstract

The studies on the decay of the pH difference, ΔpH, across soyabean phospholipid vesicular membrane have shown that the rates of net proton transport and the associated Li + and Na + ion transport across the membrane can be enhanced by the combined action of gramicidin, valinomycin and carbonyl cyanide m-chlorophenylhydrazone (CCCP) in K +-free vesicle solutions. The data obtained under different experimental conditions suggest that this enhancement is a consequence of facilitation of CCCP − transport (1) by complexing CCCP − with the highly membrane permeant valinomycin without the metal ion bound to it and (2) by the associated Li + or Na + transport through the gramicidin channel such that no net charge is transported across the membrane. The dissociation constant of the weak valinomycin-CCCP − complex has been estimated to be >200 mM in the membrane. The ΔpH in these experiments were created by temperature jump.