The binding potential between the cholera toxin B-oligomer and its receptor

Employing atomic force microscopy as an in situ molecular force probe, we have measured the binding strength between cholera toxin B-pentamer (ctB) and its membrane receptor, ganglioside G(M1). By application of the basic principle of the reaction rate theory, key parameters of the ligand-receptor binding potential can be obtained from our data. The potential has a well with a spatial span of about 2.5 A and a depth of at least six times the thermal energy at room temperature. The very short range nature of the binding potential leads to the specificity of the ctB-G(M1) coupling.