The subunit structure of the hemocyanin from the crayfish Jasus edwardsii

The hemocyanin from the crayfish Jasus edwardsii(=lalandii) has been studied using ultracentrifugation, viscosity, circular dichroism and oxygen binding techniques. Sedimentation velocity experiments at pH 7.0 indicated the presence of principal species with S 20w=16.4 S, and at higher pH the presence of a species with S20,w=5.2S. Sedimentation equilibrium experiments yielded molecular weights of 490 000 and 81 000 respectively, indicating that the larger unit is a hexamer of the monomer unit. However, preliminary experiments with gel filtration and electrophoresis under denaturing conditions indicate that more than one monomer species may be present with molecular weight in the range 76-100 000. Circular dichroism (CD) spectra are presented at pH 7.0,8.6,10.0 and 11.0 for oxy-, deoxy- and apo-hemocyanins. Slight differences were observed in the magnitude of the bands in the presence or absence of Mg++. Oxygen binding studies have been made at pH 6.1,7.0,8.8 and 10.6, in the presence of 0.01 M MgCl2. The extent of cooperative binding was indicated by a maximum value of n=3.7, and a pronounced bohr effect was observed.