Fig. 1.

Activity of FNR proteins with Phe substitutions at residues adjacent to essential Cys ligands. Plasmid pGS24 was subjected to QuikChange site-directed mutagenesis (Stratagene) to create Phe substitutions and introduced to JRG1728 (fnr lac) containing pFF-41.5, a plasmid with an FNR-activated promoter fused to lacZ. The activity of chromosomally encoded FNR (cFNR) is shown for comparison. Cultures were grown in L broth under aerobic (filled bars) or anaerobic (open bars) conditions. The mean β-galactosidase activities in Miller units (MU) and standard deviations are shown (n = 9). The line indicates the amount of aerobic activity associated with wild-type FNR overproduced from pGS24.