Abstract
The first crystal structure of phosphoenolpyruvate carboxylase (PEPC) has been determined by X-ray diffraction methods at 2.8 Å resolution using Escherichia coli PEPC complexed with L-aspartate, an allosteric inhibitor of all known PEPCs. The four subunits are arranged in a "dimer-of-dimers" form. The location of the catalytic site is suggested to be near the C-terminal side of the β-barrel. The binding site for L-aspartate is located about 20 Å away from the catalytic site and four residues (Lys773, Arg832, Arg587 and Asn881) are involved in effector binding. Considering the catalytically essential Arg587 is in a highly conserved glycine-rich loop, which is characteristic of PEPC, it seems that L-aspartate causes inhibition by removing this glycine-rich loop from the catalytic site.
