Characteristic features of Fdx of the AlvinFdx family. (A) Sequence alignment of selected 2[4Fe-4S] Fdxs from γ-proteobacteria Pseudomonas aeruginosa PAO1, Allochromatium vinosum DSM180, Escherichia coli K12-MG1655; δ-proteobacteria Anaeromyxobacter dehalogenans 2CP-C, Plesiocystis pacifica SIR-1; ε-proteobacteria Helicobacter pylori 26695, Campylobacter jejuni NCTC 11168, Cj0354 sequence; Chloroflexi Dehalococcoides sp. VS; β-proteobacteria Azoarcus sp. (or Aromatoleum aromaticum) EbN1 (locus NT01AE0820), Thauera aromatica K172; α-proteobacteria Rhodopseudomonas palustris CGA009; Clostridium acidurici as an example of heterotrophic anaerobic bacteria; Azoarcus sp. EbN1 (locus NT01AE3314) belonging to the bcr cluster; Campylobacter jejuni NCTC 11168 Cj0333 sequence. n X stands for insertions of n aminoacids. Stars on the consensus line for proteins of the AlvinFdx family indicate identical residues and colons are for conserved residues. The ① and ② symbols lie under non-conserved residues belonging to the fragment between cysteine ligands and the turn and helix addition, respectively, that characterize the AlvinFdx family as indicated in the structure of Figure 1B. The lengths of the compared sequences are given at the end of the alignment, and [4Fe-4S] cysteine ligands are boxed. (B) View of the P. aeruginosa Fdx structure . The general fold is shown (light grey tube) with the 8 amino acid stretch between two cysteine ligands of one cluster (labelled ①) and the turn and helix at the C-terminus ② colored in dark grey. Iron and inorganic sulfur atoms are represented as spheres.