The rôle of non-covalent forces in micelle formation by vicilin from Vicia faba. The effect of pH variations on protein interactions

Abstract

The influence of environmental pH on the capacity of vicilin from fababeans to self-associate into a micelle arrangement was investigated. Various types of micelle-based protein interactions were identified; these responses were related to certain vicilin conformational parameters, specifically, thermal stability and surface hydrophobicity (So). The most extensive micelle responses were observed from pH 6·0 to 6·8; a gradual deterioration in the degree of protein self-association occurred with pH increases from 6·8 to 8·0. These results corresponded with significant decreases in vicilin So, i.e. from 296 at pH 6·5 to 158 at pH 8·0. Thermal parameters over this range reflected minimal conformational disturbances. The observed importance of molecular surface hydrophobicity was supportive of the original premise that micelle structures are products of hydrophobic associative forces.