Chemical modifications of the Na+– H+ antiport in Escherichia coli membrane vesicles

Abstract

The effects of chemical modifications of the Na+– H+ antiport in Escherichia coli have been analyzed by studying the resulting variations of the energy‐dependent, downhill Na+ efflux from membrane vesicles. The histidyl reagent diethylpyrocarbonate (EtO)2C2O3 prevents the activation of the Na+ efflux mechanism by ΔH+ or its components. Inactivation of the antiporter by (EtO)2C2O3 is completely reversed by hydroxylamine. The data suggest that histidine residues are involved in the molecular mechanism of the Na+– H+ antiport. In contrast, no conclusive evidence suggesting participation of carboxylic, tyrosine or sulfhydryl residues in the Na+– H+ exchange reaction has been obtained. Copyright © 1985, Wiley Blackwell. All rights reserved