Reconstitution of energy-dependent transhydrogenase in ATPase-negative mutants of Escherichia coli

The aerobic-driven and ATP-driven energy-dependent transhydrogenase activities of membrane particles from two different Ca²⁺, Mg²⁺-activated ATPase-negative mutants of $\text{E.}$$\text{coli}$ were examined. The activities were low or absent in one of the mutants (DL-54). Reconstitution of the aerobic-driven reaction could be obtained by addition to particles from this mutant of DCCD or of a coupling factor prepared from the parent strain. The coupling factor also restored the ATP-driven reaction. In the other mutant (N144) the aerobic-driven activity was unimpaired, and was not affected by DCCD or by the coupling factor. The difference between the two mutants could be rationalized if the coupling factor ATPase had both a stabilizing and an enzymic function.