FIG. 1.

Alignment of the N-terminal regulatory domains of FNR from E. coli (23), HlyX from A. pleuropneumoniae (5), CydR from A. vinelandii (30), FnrL from R. sphaeroides (31), FixK from B. japonicum (1), and FnrP from P. denitrificans (25). The alignment is not intended to be exhaustive but rather to show examples of proteins from the gamma and alpha subdivisions of the proteobacteria for which some biological information is available. Cysteine residues of FNR known to be essential for activity are indicated (+), as are the cysteine residues of FnrP shown in this study to be essential (*). Residues of FNR that can be substituted with effects on oxygen sensitivity and that are discussed in the text are indicated (§).