Hemocyanin of Octopus vulgaris. The molecular weight of the minimal functional subunit in 3 M urea.

In the presence of 3 M urea Octopus vulgaris (Mollusca) hemocyanin dissociates completely, giving a single functional component which reassociates in the original aggregate after removal of urea. The molecular weight of this subunit has been determined by gel filtration, by viscosity measurements, and by ultracentrifugation. The values obtrained with the different methods range from 247,000 to 262,000. Electron microscopy shows that the reassociation of the functional subunit after removal of urea is complete and gives the typical cylindrical structure of the native protein. This component is the minimal functional subunit which can be obtained from Octopus hemocyanin without splitting covalent bonds. It is suggested that this component is made by five protomers (50,000 daltons) containing one oxygen binding site each bound covalently through, perhaps, the carbohydrate moieties of the protein.