Charge heterogeneity of cholera toxin and its subunits

Summary

Analytical isoelectric focusing (IEF) in thin layers of polyacrylamide gels resolved cholera toxin into 3 isomeric forms differing in charge (isoelectric points 6.80, 6.65 and 6.55). All these forms had identical molecular weights, and were also antigenically similar, as demonstrated by their reactivity to antisera to cholera toxin. Both the B and A subunits possessed charge heterogeneity. The B subunit was detected in a free form when a solution of cholera toxin was aged for a few days. Antisera to cholera toxin, irrespective of mode of immunisation, contained antibodies to both the intact cholera toxin and the free B subunit as demonstrated by the immunoblotting technique based on IEF.

Cholera toxin, isoelectric focusing