Subunit structure and dissociation of Homarus americanus hemocyanin. Effects of salts and ureas on the acetylated and unmodified hexamers

At neutral pH and in the presence of divalent cations the hemocyanin of the lobster Homarus americanus exists largely as a dodecamer with a molecular weight of 940,000. Light-scattering investigation has shown that the dodecamers dissociate to hexamers followed by dissociation of the hexamers to monomers. In the absence of calcium ion, both the acetylated hemocyanin at pH 7.8 and the unmodified protein at PH 8.8 were found to be largely in the hexameric state, with molecular weights close to 450,000. The effects of various salts of the Hofmeister series and the urea-series on the subunit organization and dissociation of the basic hexameric unit were investigated and analyzed.