In vitro interaction of groundnut proteins with aflatoxin B-1

The interaction of AFB(1) with the three major protein fractions from peanut, namely, arachin, conarchin II and conarchin I, was studied from a thermodynamic point of view. Addition of AFBT quenched the intrinsic fluorescence of all the three proteins. The association constants of the interaction were 3.5 +/- 0.4 x 10(4), 4.8 +/- 0.5 x 10(4) and 23.0 +/- 3.0 x 10(4) M(-1.) respectively with arachin, conarachin II and conarachin I at 26 degrees C. There was an increase in the beta structure content of arachin and conarachin II upon addition of AFB(1.) while an increase in aperiodic content of conarachin I was observed. The fast kinetics of the interaction yielded a pseudo first order rate constant of 54 +/- 4 sec(-1) for the three proteins. Modification of lysyl residues by succinylation decreased the strength of binding of AFB(1) with conarachin I and conarachin II by a Delta Delta G degrees = 0.4 kcal/mol, while there was no significant effect on arachin.