Sequences and structure comparisons between Clonorchis sinensis myoglobin ( Cs Mb) and its orthologues. (A) The amino acid sequence of Cs Mb was aligned with those of related proteins, which were retrieved from the GenBank database by BLAST searches (Sequence information shown in Additional file 1: Table S1). The red boxes indicate active tyrosine. (B) The tertiary structure of Cs Mb was simulated by the Discovery Studio 3.5 Client program and compared with P. epiclitum hemoglobin (Protein Data Bank id: 1KFR; 40% identity). Regions around the active site are shown in yellow indicating the positions of critical amino acids (red boxes in panel A). (C) Phylogenetic analysis. The majority-role consensus tree was derived from a neighbor-joining tree of the amino acid alignment, which was constructed by the PHYLIP program. The homologues from euryarchaeota were included in the root of the tree. Arabic numerals at branching nodes indicate their percentages of appearance in 1000 bootstrap replicates.