MECHANISTIC STUDIES USING AN INACTIVE F420-DEPENDENT GLUCOSE-6-PHOSPHATE DEHYDROGENASE VARIANT FROM M.TUBERCULOSIS
Abstract
Mycobacterium tuberculosis (Mtb) is the causative agent of one of the deadliest diseases in the world, Tuberculosis (TB). F420-dependent glucose-6-phosphate dehydrogenase (FGD) is a prime target for TB-related treatments because it is found within Mtb and utilizes the F420 cofactor, which is not found in humans. The conversion of glucose-6-phosphate (G6P) to 6-phosphoglutalactone and concurrent reduction of the F420 cofactor is carried out by FGD (Figure 1). Until our work, F420-dependent enzymes have not been subjected to rigorous enzymological investigation. Although several key pieces of information regarding FGD’s hydride transfer mechanism have been unraveled, the binding location of G6P within FGD’s active site has yet to be found. Past x-ray crystallographic studies of the Mtb-derived FGD were solved in the presence of the competitive inhibitor, citrate. To date, the position of the native substrate, G6P, is unknown. Therefore, the objective of this project is to solve the crystal structure of the enzyme-substrate complex in the presence of F420 cofactor, or with the G6P analog, 1,5-anhydro-D-glucitol 6-phosphate. We have optimized crystallization conditions using the inactive FGD variant, H40A. Several conditions of interest, using the screens provided by Hauptman Woodward Medical Research Institute, will be discussed.