The Origin of Substrate and Product Specificities of Protein Lysine Methyltransferase Suv4-20h2
【摘要】：Protein lysine methyltransferases(PKMTs) catalyze the methylation of lysine residues on the tails of histone proteins. In contrast to many other PKMTs for which unmodified lysine is the methylation target, the enzymes in the Suv4-20 family are able to generate di-methylated product(H4K20me2) based exclusively on mono-methylated H4K20 substrate(H4K20me1). Molecular dynamics(MD) and free energy simulations based on quantum mechanical/molecular mechanical(QM/MM) potentials are performed here to understand the specificity for Suv4-20h2. It is demonstrated that the reason for the relatively efficient di-methylation reaction with H4K20me1 is the effective transition state(TS) stabilization through the strengthening of CH···O interactions as well as the presence of cation-π interaction at the transition state. The simulations also suggest that the failure of Suv4-20h2 to catalyze mono-and tri-methylation is due to less effective TS stabilization for mono-methylation and inability of the reactant complex with the H4K20me2 substrate to adopt a reactive(near attack) configuration for tri-methylation.