Factors affecting the molecular structure and the agglutinating ability of concanavalin A and other lectins

Ultracentrifugation analyses were performed on lectins under varying conditions of pH, ionic strength and temperature. It has been demonstrated that the phytohemagglutinin from Phaseolus vulgaris, the wheat germ agglutinin and the soybean agglutinin are stable when these parameters are varied, whereas the concanavalin A molecule exhibits a striking reversible dimer-tetramer transition with variation in pH (from 6.0 to 7.2) and temperature (from 4 degrees up to 37 degrees C). It has also been demonstrated that, in agglutination experiments undertaken at different temperatures, cells do eventually aggregate with the first three lectins provided that incubation time is sufficient, whereas the concanavalin-A-induced agglutination was previously found to be temperature-sensitive. These results strongly suggest that the effect of temperature on agglutination by lectins may essentially be due to a structural transition of the lectin itself and nott only to modification of cell surface properties.