Dissociation of M- and N-group mucoproteins in subunits in detergen solutions

Abstract

In alkyl sulfate detergents the M- and N-group antigen mucoproteins having a molecular weight of about 10⁶ Daltons dissociate into subunits. Their molecular weight at infinite dilution was determined as 3·10⁴ Daltons. At finite mucoprotein concentrations a dynamic association-dissociation equilibrium between the subunits was observed. On dissolving in dimethylformamide-formic acid mixture (9:1 v/v), the M and N mucoprotein macromolecules disintegrated into fragments with a molecular weight of about 9·10⁴ Daltons. Removal of the detergent from the dissociated mucoprotein resulted in reaggregation of the subunits, and the material exhibited unchanged serological activity. The observations suggest that in water solutions the subunits are kept in aggressive forms by hydrophobic bonds. This may be caused by asymmetric distribution of hydrophilic residues (sugars, amino sugars, and sialic acid) along the polypeptide backbone of the subunits.