| Research Abstract |
Annelid extracellular hemoglobin is a supramolecule with molecular mass of ~3,500kDa. The giant hemoglobin consists of four types of total 144 globin chains and 36 linkers. In the present project, the amino acid sequences of globins a, A, b, and B of the giant hemoglobin from the polychaete Perinereis aibuhitensis have been determined by the combination of Edman degradation and RT-PCR method. The primary structures of Perinereis globin chains are compared with those of globins reported by others. From the point of view of structure and function of the giant annelid hemoglobins, we have noticed particularly at the cites of Cys residues in the amino acid sequences. There are 6 cites for the Cys residues in 32 sequences derived from the various giant hemoglobins. There are two Cys cites in the N-terminal region (cite 1, 2), two in the central region (cite 3, 4), one near the C-terminal region (cite 5), and one in the C-terminal region (cite 6). Cys residues are conserved in the cite 2 and 6. It has been also confirmed that Cys residues of the globins are all linked each other. Therefore, the Cys residues are all participated in the formation of SS bridges. The Cys sites of 32 sequences were categorized into 8 patterns: I (cite 2, 6), II (2, 4, 6), III (2, 4, 5, 6), IV (2, 5, 6), V (2, 3, 5, 6), VI (1, 2, 3, 5, 6), VII (1, 2, 5, 6), and VIII (1, 2, 6). The molecular phylogenetic tree of 32 globin sequences is divided into two branches of family A and B. The family A includes the types I, II, III, VI, VI of Cys distribution pattern, whereas the family B includes the types V, VI, VII, VIII. The relationship between the Cys distribution pattern and molecular adaptation has been discussed.
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