Hemocyanin: The Evolution of a Protein

Speaker: Erin K. van Olden

This project is the culmination of over 20 years research on Octopus dofleini hemocyanin. The work began by characterizing this oxygen binding protein, a decamer of 3.5 million M.W. The molecule is comprised of 10 subunits, each containing seven copper oxygen binding sites. Subsequent studies have revealed the protein structure and function, bringing us to where I entered the project—the sequencing of the gene. Completion of the Octopus gene sequence, along with the completion of the Haliotis gene by our colleagues in Germany, will allow a greater understanding of evolutionary relationships between the molluscs and gastropods.
The Octopus gene is ~13 Kb long and codes for ~3000 amino acids. Like the protein, the gene is arranged in a “string of beads” formation. The protein sequence for each of the oxygen binding units is separated by a short linker region. The gene contains phase one introns at the beginning of every linker region, as well as introns in the middle of three of the functional units.
To further our knowledge of the evolution and divergence of this protein, we have chosen the Chambered Nautilus as our next sequencing project. Nautilus pompilius is a very ancient cephalopod. Comparisons of its sequence to the already completed Octopus and Haliotis sequences will give a more complete picture of the evolution of hemocyanin.