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Sequence of the Octopus dofleini hemocyanin subunit: structural and evolutionary implications
K I Miller1, M E Cuff, W F Lang
1Department of Biochemistry and Biophysics, Oregon State University Corvallis 97331, USA.
Journal of Molecular Biology
|June 6, 1998
Summary
The complete hemocyanin protein sequence from Octopus dofleini was determined, revealing seven functional units with conserved copper-binding sites. This provides insights into the evolution of molluscan hemocyanins.
Area of Science:
- Biochemistry
- Molecular Biology
- Evolutionary Biology
Background:
- Hemocyanins are copper-containing respiratory proteins found in mollusks and arthropods.
- Octopus hemocyanin is a complex multimeric protein crucial for oxygen transport.
Purpose of the Study:
- To achieve the complete sequencing of a hemocyanin subunit from Octopus dofleini.
- To analyze the structure, functional units, and evolutionary relationships of molluscan hemocyanins.
Main Methods:
- cDNA library construction and sequencing.
- Bioinformatic analysis of protein sequences.
- Comparative sequence analysis with other hemocyanins.
Main Results:
- The complete sequence of an Octopus dofleini hemocyanin subunit (2896 amino acids) was determined, comprising seven functional units.
- Conserved histidine residues form copper-binding sites (A and B) within each unit.
- High sequence similarity (approx. 40% identity) among functional units and homology of B-site regions with arthropod hemocyanins were observed.
- Putative N-linked glycosylation sites were identified, with one corresponding to experimentally observed carbohydrate attachment.
Conclusions:
- Octopus hemocyanin subunits are composed of repeating, similarly folded functional units.
- The multi-domain structure of molluscan hemocyanins likely evolved rapidly.
- Sequence homology suggests evolutionary links between molluscan and arthropod hemocyanins.