Figure 2. Phylogenetic Tree of α-Proteobacterial Regulators from the Fur Superfamily.

(A) Fur/Mur, (B) Irr. Experimentally characterized regulatory proteins are in bold and boxed. Positional clustering (i.e., close linkage) of the mur genes with the target manganese uptake sit operons is shown by background grey. Irr proteins with the heme regulatory motif (see text) at their N-termini are marked with asterisks. Functional annotation of the “mur” and “fur^α” regulators is based on the genomic analysis of their candidate regulatory motifs that occur in 5′ regions of either manganese or iron uptake genes, respectively. Possible role of the B. japonicum regulator Fur in the control of the manganese uptake gene mntH was predicted in this study and is not yet proved.