A new theoretical approach to the investigation of the symmetry of protein oligomers with bifunctional reagents

The use of bifunctional reagents to form cross-links between subunits in protein oligomers and subsequent disruption of noncovalent interactions with SDS allows comment upon the number of subunits and the symmetry in the original assembly. In existing treatments the number of equations needed to describe theoretically the proportions of all the cross-linked species that can be formed as a function of time in this way makes the analysis of the system unmanageable for proteins with more than four subunits. A method is presented that allows the required equations for any oligomer to be formulated as an algorithm suitable for solution by computer. Its application is illustrated with reference to experimental results obtained with two protein hexamers, Jasus hemocyanin and alpha-urease from jack bean.