Final Answer:
The binding of proteins A and B to form the complex AB under equilibrium is driven by thermodynamic forces, resulting in a stable, balanced state.
Step-by-step explanation:
Protein-protein interactions are governed by thermodynamics, particularly through free energy changes. When proteins A and B associate to form the AB complex under equilibrium, it implies that the forward and reverse reactions occur at equal rates, signifying a stable state. This equilibrium is dictated by factors such as enthalpy, entropy, and temperature.
The binding process involves favorable interactions between complementary regions on proteins A and B, leading to a decrease in free energy. The enthalpic contribution involves hydrogen bonding, van der Waals forces, and electrostatic interactions. Meanwhile, entropy plays a role by allowing water molecules to organize around the complex.
At equilibrium, the Gibbs free energy change (ΔG) is zero, indicating that the system is in a state of minimum free energy. The equilibrium constant (K_eq) provides insight into the ratio of concentrations of AB complex to individual A and B proteins. Factors influencing the equilibrium, such as temperature and concentration, impact the stability of the AB complex.
In summary, the formation of the AB complex under equilibrium is a dynamic process where thermodynamic forces govern the balance between association and dissociation, resulting in a stable, energetically favorable state.