CONFORMATION AND ACTIVITY OF PHASEOLUS-COCCINEUS VAR RUBRONANUS LECTIN

The conformation of native and denatured Phaseolus coccineus var. rubr onanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25-degrees-C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a beta-sheet-rich protei n. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activit y. The conformation of lectin between pH 2 and 10 remained essentially unchanged. At pH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renature d upon diluting the denaturant to 0.75 M; the changes in CD spectrum a gain correlated well with the loss of the activity. The effect of sodi um dodecyl sulfate on the lectin was drastic; it sharply increased the alpha-helix at the expense of the beta-sheet and reduced the activity ; the changes reached a plateau above 20 mM surfactant.