Lysozyme dimerization: Brownian dynamics simulation.

The lysozyme dimerization reaction has been studied within the framework of encounter-complex (EC) formation theory using the MacroDox software package. Two types of energetically favorite ECs were determined. In the first of them, active-center amino acids of lysozyme take part in the complex formation or the second molecule blocks accessibility to active center sterically. Epitope amino-acid residues are involved in the complex of type II. The existence of both types of complexes does not contradict experimental data. Dimer-formation rate constants for different kinds of EC were calculated. Increasing the pH from 2.0 to 10.0 decreases the total positive lysozyme charge and eliminates the unfavorable repulsive electrostatic interaction. The rate constant of EC formation is inversely proportional to the protein total charge. The association rate constant was also enhanced by an increase of ionic strength that screened repulsive electrostatic interaction between positively charged proteins.