FIGURE 2.

Speculative topology of the E. coli NuoH subunit. The prediction has been performed on the basis of a composite of computer programs, including the reported topology of its Rhodobacter counterpart (31). The eight transmembrane segments of the E. coli NuoH subunit from the N terminus to the C terminus are designated TM1–8. The four cytoplasmic side loops are marked as C1–C4, whereas P1–P3 represent three periplasmic side loops. The N and C terminus of the subunit are exposed to the periplasmic side of the membrane. Amino acid residues mutated in this study are displayed as black squares, and some are marked by their E. coli numbering.