Presenting Author Virginia Tech Blacksburg, Virginia, United States
Rowan Wooldridge (Virginia Tech)| Kylie Allen (Virginia Tech)
Folate is an essential cofactor required for several processes including DNA and amino acid biosynthesis. Folate molecules are made up of three parts: a pteridine ring, p-aminobenzoate (pABA), and a variable number of glutamate residues. Chlamydia trachomatis synthesizes folate de novo; however, several genes encoding enzymes required for the canonical folate biosynthesis pathway are missing, including PabA/B and PabC, which are normally required for pABA biosynthesis from chorismate. Previous studies have found that a single gene in C. trachomatis, CT610, functionally replaces the canonical pABA biosynthesis genes. Interestingly, CT610 does not use chorismate as a substrate. Instead, the CT610-route for pABA biosynthesis incorporates isotopically-labeled tyrosine into the synthesized pABA molecule. However, in vitro experiments revealed that CT610 produces pABA without any added substrates (including tyrosine) in the presence of a reducing agent and molecular oxygen. CT610 shares low sequence similarity to non-heme diiron oxygenases and the previously solved crystal structure revealed a diiron active site. Taken together, CT610 is proposed to be a self-sacrificing “suicide” enzyme that uses one of its active site tyrosine residues as a precursor to pABA in a reaction that requires O2 and a reduced diiron cofactor. Here, we discuss our recent progress towards uncovering the mechanism of CT610-catalyed pABA synthesis.