Stability & Flexibility of 3‐Phosphoglycerate Dehydrogenase

Abstract

3 Phosphoglycerate Dehydrogenase is a homotetramer whose three dimensional structure has been determined both in the presence and absence of the allosteric regulator Serine. Prior work in the laboratory has shown that D264 in the active site plays a critical role in both activity and serine regulation. The serine binding sites are located at one of the two tetramer interfaces, well away from the active sites which are located near the other tetramer interface. This raises the question as to what types of conformational changes are involved in transmitting serine inhibitory effects to the active site. To probe the role that protein dynamics may play in this effect we have investigated the effects of serine on Guanidine Hydrochloride denaturation using the fluorescence of the single tryptophan per polypeptide chain to monitor conformation, and correlated the unfolding transitions with subunit dissociation transitions, obtained using fluorescence polarization under the same conditions. In an attempt to determine whether or not there are local changes in dynamic properties of the protein induced by serine we have examined the temperature factors obtained in the various X ray structures of the E Coli protein in the presence and absence of serine. Limited proteolysis experiments are underway to experimentally locate flexible regions of the protein and to determine whether or not serine causes changes in local flexibility of the protein. This work is supported by NSF Grant MCB 0448905 to EB.