Sequence alignment of the C-terminal region of the NrdD polypeptide containing the four almost completely conserved cysteine residues. Totally conserved residues are shown in black boxes. The secondary structure as observed in the crystal structure of NrdD from bacteriophage T4 is shown on the top line. T = turn. Figure generated by using ESPRIPT (43). Key to sequence names: Bp_T4, bacteriophage T4; S_mut, Streptococcus mutans; S_pyo, Streptococcus pyogenes; L_lac, Lactococcus lactis; E_fae, Enterococcus faecalis; S_auC, Staphyloccocus aureus COL/NCTC; V_cho, Vibrio cholerae; H_inf, Haemophilus influenzae; S_put, Shewanella putrefaciens; Y_pes, Yersinia pestis; E_col, Escherichia coli; S_typ, Salmonella typhimurium; C_ace, Clostridium acetobutylicum; P_aby, Pyroccocus abyssi; P_hor, Pyrococcus horikoshii; M_jan, Methanococcus jannaschii; M_the, Methanobacterium thermoautotrophicum; A_eut, Alcaligenes eutropha (Ralstonia eutropha); P_aer, Pseudomonas aeruginosa; C_dip, Clostridium difficile.