Figure 4.

Stability of the HelABC complex in HelC mutant strains. The stability of the HelABC complex was determined by analyzing the presence of the HelA protein by immunoblot of R. capsulatus ΔhelC strains containing plasmids carrying either the wild type or mutated helC gene. Lanes: 1, 2, and 4–8, equal amounts of membrane fractions (∼40 μg of protein per lane); 3, ∼20 μg of protein per lane of membrane fraction. The fractions were separated by PAGE on a 15% gel. The helC mutations were present on a plasmid and were tested in the strain ΔhelC. Lanes: 1, ΔhelABC; 2, ΔhelC; 3, pHelC H58G/ΔhelC; 4, pHelC H183G/ΔhelC; 5, pHelC G118A/ΔhelC; 6, ΔhelD; 7, pHelC WT/ΔhelC; 8, SB1003 (Wild type). Light bands above the HelA protein in lanes 5, 7, and 8 are c-type cytochromes. The covalently bound heme of these proteins generates a signal in the ECL assay.