FIG 4.

Aconitase and fumarase activity of E. coli Δric and Δdps mutant strains. Aconitase activity of E. coli wild-type, Δric, Δdps, and Δdps Δric strains grown aerobically to OD₆₀₀ of 0.6 (A and D) or 2.0 (B). Fumarase activity of E. coli wild-type, Δric, Δdps, and Δdps Δric strains grown aerobically to an OD₆₀₀ of 0.6 (C). Complementation experiments of aconitase activity (D) were performed using Δric and Δdps Δric strains transformed with pUC18, and with pUC18 encoding the RIC protein and the mutated Glu133Leu-RIC (a RIC protein where glutamate 133 underwent site-directed mutation by leucine [10]). Values are represented as normalized to the aconitase or fumarase activity of wild-type cells. Values are means (±standard errors) from at least two independent cultures analyzed in duplicate. *, P < 0.05; **, P < 0.005; ns, not significant (unpaired Student's t test).