Kinetic parameters of polyreactive immunoglobulins interaction with antigens in the presence of protamine

The discovered earlier phenomenon of the enhancment of polyreactive immunoglobulines (PRIGs) binding to antigens in the presence of protamine and Tween 20 was investigated in more details. The comparative analysis of PRIGs reaction dynamics with immobilized antigen was provided. In addition, the rate constants for the reaction and the affinity constants of PRIGs-antigen binding in the presence or absence of optimal protamine concentration were determined. The rate constant of PRIGs-antigen reaction did not increase in the presence of protamine optimal concentration and was even reduced approximately twice. However, in the presence of protamine the concentration of reactive PRIGs molecules, that were able to interact with antigen, increased approximately 30 times, and this led to strong reaction rate increase. Protamine also influenced the affinity constant of PRIGs-antigen binding, which increased approximately three times. The suggestion was made that such protamine effect was due to its influence on the PRIGs molecules special structure, and, as a result of the conformational change PRIGs became able to bind more effectively to the antigens.