Amino acid sequence of a major globin from the sea cucumber Paracaudina chilensis

The sea cucumber Paracaudina chilensis (Echinodermata) contains three major globins I, II and III in coelomic cells. The complete amino acid sequence of globin I has been determined. It is composed of 157 amino acid residues, is acetylated at the N-terminus, and has a characteristic N-terminal extension of 9-10 residues when compared with vertebrate globins. The sequence of Paracaudina globin I showed slightly higher homology with human alpha globin (25%) rather than with the invertebrate Anadara alpha globin (22%). Paracaudina globin I also showed strong homology (59%) with globin D from another sea cucumber, Molpadia arenicola (Mauri, F.C. (1985) Ph.D. dissertation, University of Texas). The globin sequences from the phylum Echinodermata have an important position in the molecular evolution of the globins, because they are the invertebrate group most closely related to the vertebrates.