Fig 1

A. The amino acid sequences of the C. sinensis proteins were aligned with those of Physeter catodon, of which the tertiary structure was empirically determined (PDB no. 1A6M), and Danio rerio orthologs. The degree of amino acid conservations was highlighted by different shades of grey, and gaps were introduced in the alignment to increase the similarity values. The amino acid positions involved in the binding of heme and oxygen molecules are marked with solid arrowheads and circles (see text). Secondary structure elements determined in the P. catodon globin are shown on the top of the alignment (-, no secondary structure assigned; S, bend; T, turn; G, 3/10-helix; H, alpha-helix). B. A phylogenetic tree of C. sinensis globins and their orthologs. The maximum likelihood tree was constructed using PhyML based on the sequence alignment of globin domains and was rooted in CsFbH. C. sinensis proteins are highlighted in boldface. Branch support values > 0.50, which were obtained by the Shimodaira-Hasegawa-like approximate likelihood ratio test, are indicated at the corresponding branching nodes. The solid arrowhead indicates an evolutionary point where the progenitor of the platyhelminth Mb gene might have been duplicated.