| Chlamydia trachomatis depends on a eukaryotic host cell for the acquisition of many metabolic precursors including nucleotides. With the exception of thymidylate, the mode of acquisition of all nucleotides required for RNA and DNA biosynthesis in chlamydiae has been elucidated. The only known mechanisms of thymidylate acquisition are the de novo synthesis, by thymidylate synthase (thyA) or the salvage of thymidine from the environment by thymidine kinase (tk). In Escherichia coli, thyA catalyzes the reductive methylation of deoxyuridine 5' -monophosphate (dUMP) by methylenetetrahydrofolate (CH2H 4folate) to form dTMP and dihydrofolate (H2folate). Interestingly, comparative genomic analysis indicates that several bacteria, including Chlamydia sp., lack both the known pathways for formation of dTMP suggesting an alternative method of acquisition. In Helicobacter pylori a novel enzyme (ThyX) has recently been shown to catalyze dTMP formation from dUMP. The goals of this thesis were to provide molecular and biochemical evidence for the existence of a thymidylate-synthesizing enzyme within chlamydiae and to characterize this novel enzyme. (Abstract shortened by UMI.)... |
