A transient kinetic study between signaling proteins: the case of the MEK–ERK interaction

MEK and ERK are central components of the mitogen-activated protein kinase pathway. However, an accurate interaction has never been studied and accurate binding constants of the binary interaction have never been directly measured. In the present work, we studied the interaction between MEK and ERK by stopped-flow fluorescence intensity and evaluated the association and dissociation rate constants (kon and koff) from the kinetic study. We compared the results obtained by using commercial and homemade protein productions. The dissociation binding constant (Kd) value determined for the binding of MEK to ERK is in good agreement with the values obtained from the analysis of the kinase enzymatic reaction in previous in vitro studies.