Hemocyanin from the Australian freshwater crayfish Cherax destructor. Characterization of a dimeric subunit and its involvement in the formation of the 25S component.

The molecular weight of a dimeric subunit, M3', isolated from Cherax destructor hemocyanin has been measured by sedimentation equilibrium to be 144 000. Peptide mapping and end-group analysis together with gel electrophoresis show that the dimer consists of two very similar or identical monomers, cross-linked by disulfide bridges. Dissociation of the 25S component of the hemocyanin shows that it contains the dimer and two previously identified monomers, M1 and M2. Its molecular weight is 900 000 by sedimentation equilibrium, and reconstitution studies show that the dimer is essential for its formation. Analysis of the results of polyacrylamide disc gel electrophoresis experiments with the 25S component indicates that it consists of a population of 11 compositional isomers. These all contain one dimeric subunit and ten monomeric subunits, the latter being present in all the combinations of M1 and M2.