Sequential assignments of the isolated N-terminal domain of 5-enolpyruvylshikimate-3-phosphate synthase.

5-Enolpyruvylshikimate-3-phosphate (EPSP) synthase catalyzes the formation of EPSP from shikimate-3phosphate (S3P) and phosphoenolpyruvate (PEP) in the sixth step of the shikimate pathway. This pathway is absent from mammalian systems but present in plants, bacteria, fungi and parasites, making EPSP synthase a promising model for the development of new antibiotics. One suggested approach toward inhibitor design is the prevention of domain closure, an event that is necessary for catalysis. However, what triggers domain closure is in question due to conflicting crystal structures of the enzyme •S3P complex. One shows the enzyme in the open state, with S3P bound only to the N-terminal domain, while the other has S3P in contact with residues of both domains and the enzyme in the closed state. We have prepared the isolated domains of EPSP synthase in order to analyze the individual contributions of the domains to the events of substrate binding and catalysis. In particular, isolation of the N-terminal domain will allow us to differentiate between the chemical shift effects of S3P binding and those of domain closure, which will provide a very specific basis for designing inhibitors of domain closure. Here we report the backbone and side chain chemical shift assignments for the isolated N-terminal domain. The assignments have provided a basis for interpretation of H2O exchange experiments (Stauffer et al., 2001a) and chemical shift mapping of the S3P binding site (Stauffer et al., 2001b).