The uridylyltransferase, GlnD, and tRNA modification GTPase, MnmE allosterically control Escherichia coli folylpoly-γ-glutamate synthase, FolC.
Journal of Biological Chemistry
Folate derivatives are important cofactors for enzymes in several metabolic processes. Folate-related inhibition and resistance mechanisms in bacteria are potential targets for antimicrobial therapies and therefore a significant focus of current research. Here, we report that the activity of Escherichia coli poly-γ-glutamyl tetrahydrofolate/dihydrofolate synthase (FolC) is regulated by the glutamate/glutamine-sensing uridylyltransferase (GlnD), the THF-dependent tRNA modification enzyme (MnmE) and the UDP-glucose dehydrogenase (Ugd) as shown by direct in vitro protein-protein interactions.
Using kinetics analyses, we observed that GlnD, Ugd, and MnmE activate FolC many fold by decreasing the Khalf of FolC for its substrate, L-glutamate. Moreover, FolC inhibited the GTPase activity of MnmE at low GTP concentrations. The growth phenotypes associated with these proteins are discussed. These results, obtained using direct in vitro enzyme assays, reveal unanticipated networks of allosteric regulatory interactions in the folate pathway in E. coli and indicate regulation of polyglutamylated tetrahydrofolate biosynthesis by the availability of nitrogen sources, signaled by the glutamine-sensing GlnD protein.