Oxidative phosphorylation in mutants of Escherichia coli defective in energy transduction

Two mutants defective in oxidative phosphorylation have been isolated from Escherichia coli K12. The mutants lack ATP-driven transhydrogenase activity and exhibit P/NADH ratios, as measured in whole cells, of 0.04 and 0.16, respectively, as compared with a parental value of 2.1. Respiration-linked transhydrogenase was detected in membrane particles from the two strains. One of the mutants was defective in membrane (Mg²⁺-Ca²⁺-ATPase activity while the second strain exhibited a level of ATPase activity comparable to that in the parent. The ATPase in this latter mutant appeared to be converted to a form which is resistant to the inhibitor N,N′-dicyclohexylcarbodiimide.