Question

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B?

(a) kon/koff = K
(b) K = [A][B]/[AB]
(c) K = [AB]/[A][B]
(d) (a) and (c)

Answer 1

The correct calculation for the equilibrium constant is K = [AB]/[A][B]. This represents the ratio of the concentration of the complex AB to the product of the concentrations of A and B at equilibrium. The full correct answer including kinetic rate constants is (d) (a) and (c).

Step-by-step explanation:

If proteins A and B have complementary surfaces and can interact to form a dimeric complex AB, we aim to determine the equilibrium constant (K) for the association

The correct way to calculate the equilibrium constant for the association between A and B is represented by the formula:

Equilibrium Constant (K)

K = [AB]/[A][B]

This formula reflects the ratio of the product concentration, which in this case is the complex AB, to the product of the reactant concentrations, A and B, at equilibrium. Based on the choices provided, the correct answer is (c) K = [AB]/[A][B]. However, option (a) also presents a correct relationship, albeit in the context of kinetic rate constants, where K is the ratio of the rate constants for the forward (kon) and reverse (koff) reactions, thus (d) (a) and (c) is the full correct answer.