Influence of ligand concentration on kinetic mechanism and transition rate constant.

(A) Fractional flux of IF route () as a function of ligand concentration. Increasing ligand binding interactions can facilitate MBP to activate its conformation following an induced fit pathway. Intriguingly, is always kept on high values () during all the ligand concentrations. This strongly supports that the induced fit pathway is the predominant activation route of the system. (B) Transition rate constants as a function of ligand concentration. and increased as ligand concentration increased. However, increased more sharply than and . Our simulation results give strong support that if the transition rate between ligand-free major state and ligand-binding active state is sufficiently high, then the enzyme will mostly follow the direct conformational transition route, resulting in a predominant induced fit mechanism.