Plausible phosphoenolpyruvate binding site revealed by 2.6 angstrom structure of Mn2+-bound phospoenolpyruvate carboxylase from Escherichia coli

We have determined the crystal structure of Mn2+-bound Escherichia coli pho sphoenolpyruvate carboxylase (PEPC) using X-ray diffraction at 2.6 A resolu tion, and specified the location of enzyme-bound Mn2+, which is essential f or catalytic activity, The electron density map reveals that Mn2+ is bound to the side chain oxygens of Glu-506 and Asp-543, and located at the top of the alpha/beta barrel in PEPC, The coordination sphere of Mn2+ observed in E, coli PEPC is similar to that of Mn2+ found in the pyruvate kinase struc ture. The model study of Mn2+-bound PEPC complexed with phosphoenolpyruvate (PEP) reveals that the side chains of Arg-396, Arg-581 and Arg-713 could i nteract with PEP, (C) 1999 Federation of European Biochemical Societies.