Intracellular expression of Vitreoscilla hemoglobin alters Escherichia coli energy metabolism under oxygen‐limited conditions

Abstract

An earlier stoichiometric analysis of oxygen‐limited metabolism of Escherichia coli expressing cloned Vitreoscilla hemoglobin (VHb) suggested improved efficiency of ATP production relative to wild‐type controls [Khosla, C., Curtis, J. E., DeModena, J., Rinas, J. & Bailey, J. E. (1990) Bio‐Technol. 8, 849–853]. This hypothesis has been further examined by determining several energetic parameters of different VHb‐expressing E. coli (VHb+) strains relative to controls not expressing VHb (VHb–). The H+/O ratio, the transmembrane ΔpH, and the ATP content of VHb+ constructs are 1.5, 1.6 and 2 times, respectively, corresponding values in VHb– controls. VHb was expressed using a low‐copy‐number vector in E. coli mutant strains lacking cytochrome o, cytochrome d, or both terminal oxidases; significant growth enhancement due to VHb expression was observed only in the strain having functional cytochrome o and lacking cytochrome d. All of these data obtained using different E. coli strains are consistent with a model of VHb action that hypothesizes enhancement by VHb of activity of the lower oxygen‐affinity, higher proton‐pumping‐efficiency cytochrome o terminal oxidase under oxygen‐limited growth conditions. Copyright © 1994, Wiley Blackwell. All rights reserved