Figure 3.

Methylmenaquinol:fumarate reductase (Mfr) gene expression, protein subunit abundance and enzyme activity changes markedly in response to oxygen availability.

A. Gene expression changes during the 150% to 40% aerobiosis transition (normalised to onefold at 150% aerobiosis), showing large transient fold‐changes for the genes encoding the active‐site flavoprotein subunit (mfrA), the electron transferring iron‐sulphur protein (mfrB) and the membrane anchor containing the methylmenaquinol oxidation site (mfrE).

B. Relative abundance of MfrA, MfrB and MfrE in steady‐states at 40% and 150% aerobiosis, measured by LC‐MS/MS.

C. Correlation of MfrA abundance at each steady‐state (expressed as the fold‐change in the normalised spot volume from 2D‐gel analysis; raw data in Supporting Information Table S3) with enzyme activity (D) measured in periplasmic extracts as the rate of fumarate dependent oxidation of reduced methyl viologen (* p < 0.05 by Students t‐test). In each panel, error bars represent standard deviation of the mean.