The aim of the project to understand the structure, assembly, and physiological function of a very large multi-subunit protein, the hemocyanin of the Pacific octopus, Octopus dofleini. The functional macromolecular assemblage is a decamer of very large polypeptide chains, each of mass 3.5 x 105 daltons. Each monomer chain is folded into seven domains, each of which carries an oxygen binding site. The amino acid sequence of the monomer chain from a c-DNA library, is being determined the entire sequence. Comparison of sequences between domains will provide an unusual view of protein evolution, since tandem copies of a primitive gene are being examined. Individual domains with the intention of determining (or groups of domains) will be isolated and attempts will be made to correlate differences in oxygen binding function with sequences, and to determine what role different domains may play in the assembly process. If it proves possible to reassociate subunits from which one or more domains have been removed, the oxygen binding will be analyzed to see what extent the binding retains to cooperative character observed in the native decameric molecule. A common theme is many of these observations is the great disparty in oxygen binding between the whole decamer and its parts. What is needed are oxygen binding experiments using either dimeric structure or decamers in which one or more domain types are missing, to probe the role of parts of the structure in the functioning of the whole. It may now be possible. Another aspect of interest is evolution, how did molluscan and arthropod hemocyanins arise and independently evolve? //
