Primary sequence alignment generated by using CLUSTAL W (43) for selected proteins belonging to the Fur superfamily. Sequences shown are those from Agrobacterium tumefaciens (FurAt), Rhizobium leguminosarum (MurRl), Bradyrhizobium japonicum (FurBj), Sinorhizobium meliloti (FurSm), Escherichia coli (FurEc), and Pseudomonas aeruginosa (FurPa). Sequences were from GenBank (http://www.ncbi.nlm.nih.gov/GenBank) and accession numbers are as follows: FurAt (NP_531060), MurRl (CAA74010), FurBj (AAC32180), FurSm (CAC47604), FurEc (NP_415209), and FurPa (AAC05679). The putative regulatory Fe-sensing site residues (S1) are indicated with circles (•), and the structural Zn-binding site residues (S2) are indicated with triangles (▵).