The crystallization and preliminary X-ray analysis of allosteric chorismate mutase

The mechanism of catalysis of the chorismate to prephenate reaction by the Escherichia coli mutase enzyme

Molecular dynamics studies of the Escherichia coli chorismate mutase (EcCM), containing at the active site chorismate and in turn the transition state (TS), have been performed. The simulations show that TS is not bound any tighter than chorismate. Comparison of average polar interactions show they are virtually identical for interactions of EcCM with chorismate and the TS, whereas hydrophobic interactions with TS are much weaker than with chorismate. Interactions and the mechanism of catalysis of chorismate --> prephenate by the EcCM enzyme are discussed.

The crystal structure of allosteric chorismate mutase at 2.2-A resolution

The crystal structure of an allosteric chorismate mutase, the Thr-226-->Ile mutant, from yeast Saccharomyces cerevisiae has been determined to 2.2-A resolution by using the multiple isomorphous replacement method. Solvent-flattening and electron-density modification were applied for phase improvement. The current crystallographic R factor is 0.196. The final model includes 504 of the 512 residues and 97 water molecules. In addition, two tryptophan molecules were identified in the interface between monomers. The overall structure is completely different from the reported structure of chorismate mutase from Bacillus subtilis. This structure showed 71% helices with essentially no beta-sheet structures.