The Electrochemical Proton Gradient Generated by the Fumarate‐Reductase System inEscherichia coli and Its Bioenergetic Implications

Abstract

Proton translocation, coupled to electron transfer in the fumarate reductase system, generates and electrochemical potential gradient for protons (). The magnitude of this free energy gradient has been determined in theEscherichia coli strains ML 208–225 and AN 283. The measurements were performed in (inverted) membrane particles, right‐side out membrane vesicles and EDTA‐treated intact cells in external media of various ionic compositions and pH. The maximal values of in these three systems were +103, −101 and −105 mV, respectively. This implicates that in E. coli, upon transition from oxygen to fumarate as electron acceptor, the magnitude of the decreases considerably. This change of has substantial consequences for the cellular metabolism. Copyright © 1981, Wiley Blackwell. All rights reserved