Amino acid alignment of AMP deaminase homologues. The full-length ice worm (Mesenchytraeus solifugus ) AMPD fragment obtained in this study is represented (543 amino acids). N-terminal domains are shaded dark-gray; C-catalytic domain is shaded light gray. Periods represent conserved residues with respect to M. solifugus AMPD. Dashes indicate gaps in the linear amino acid sequence. Gray boxes represent ice worm-specific amino acid substitutions, and black boxes represent unique ice worm substitutions. Secondary structures are represented as -helices (boxes) or -sheets (arrows). Residues denoted by colored spots are explained in the legend at the bottom of the alignment. Ice worm-specific amino acid loops (V8-D24 and T129-G131, see text) are highlighted in red. GenBank accession numbers are Arabidopsis thaliana (NP 565886); Homo sapiens (NP 000027); Drosophila melanogaster (AAF48329); Caenorhabditis elegans (NP 001040752); Mesenchytraeus solifugus (EU624492); Enchytraeus albidus (EU624493), Lumbriculus variegatus (EU624494).