Energetic Effect of Vitreoscilla Hemoglobin Expression in Escherichia coli: An On‐Line 31P NMR and Saturation Transfer Study

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Abstract
A newly developed on‐line 31P NMR system has been used to investigate the effect of Vitreoscilla hemoglobin (VHb) expression on the steady‐state level of ATP in Escherichia coli under oxygen‐limited conditions. The VHb‐expressing strain GR021 exhibited a higher growth rate on a minimal fed‐batch medium after the onset of oxygen limitation and maintained the same level of ATP pool and transmembrane ΔpH as the slower growing wild‐type strain MG1655, indicating that the net ATP accumulation rate (the rate at which ATP increases per unit volume of culture per unit time) was enhanced in the VHb‐expressing strain. Further direct evidence of the enhanced flux of Pi‐ATP (catalyzed by ATPase) in GR021 was obtained in a saturation transfer study on respiring cells. VHb‐expressing cells respiring on succinate exhibited a Pi‐ATP flux 30 ± 5% higher than that of an otherwise isogenic strain that did not express VHb.

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