N-terminal amino acid sequences of 440 kDa hemoglobins of the deep-sea tube worms, Lamellibrachia sp.1, Lamellibrachia sp.2 and slender vestimentifera gen. sp.1 evolutionary relationship with annelid hemoglobins.

The deep-sea tube worm Lamellibrachia, belonging to the phylum Vestimentifera, contains two types of extracellular hemoglobins, a 3,000 kDa hemoglobin and a 440 kDa hemoglobin. The latter hemoglobin is composed of four heme-containing chains with molecular masses of 16-18 kDa. We have collected Lamellibrachia sp.1, Lamellibrachia sp.2 and Slender vestimentifera gen. sp.1 from the deep-sea cold-seep or hydrothermal areas at a depth of 1100-1400 m. The four constituent chains of the 440 kDa hemoglobin were isolated from each of the three tube worms by reverse-phase chromatography, and the N-terminal amino acid sequences of 16-44 residues were determined by automated protein sequencer. The amino acid sequences of the homologous chains showed high homology (76-85%), suggesting that they are closely related. The sequences also showed 45-49% homology with annelid hemoglobins. A phylogenetic tree constructed from hemoglobin sequences showed that the tube worm Lamellibrachia, the polychaete Tylorrhynchus and the oligochaete Lumbricus diverged from a common ancestor at almost the same time, about 450 million years before present.