Mechanistic insight into impact of phosphorylation on the enzymatic steps of farnesyltransferase

Abstract

Farnesyltransferase (FTase) is a heterodimeric enzyme, which catalyzes covalent attachment of the farnesyl group to target proteins, thus coordinating their trafficking in the cell. FTase has been demonstrated to be highly expressed in cancer and neurological diseases; hence considered as a hot target for therapeutic purposes. However, due to the nonspecific inhibition, there has been only one inhibitor that could be translated into the clinic. Importantly, it has been shown that phosphorylation of the alpha-subunit of FTase increases the activity of the enzyme in certain diseases. As such, understanding the impact of phosphorylation on dynamics of FTase provides a basis for targeting a specific state of the enzyme that emerges under pathological conditions. To this end, we performed 18 mu s molecular dynamics (MD) simulations using complexes of (non)-phosphorylated FTase that are representatives of the farnesylation reaction. We demonstrated that phosphorylation modulated the catalytic site by rearranging interactions between farnesyl pyrophosphate (FPP)/peptide substrate, catalytic Zn2+ ion/coordinating residues and hot-spot residues at the interface of the subunits, all of which led to the stabilization of the substrate and facilitation of the release of the product, thus collectively expediting the reaction rate. Importantly, we also identified a likely allosteric pocket on the phosphorylated FTase, which might be used for specific targeting of the enzyme. To the best of our knowledge, this is the first study that systematically examines the impact of phosphorylation on the enzymatic reaction steps, hence opens up new avenues for drug discovery studies that focus on targeting phosphorylated FTase.