Osmolyte control of DiHydroFolate Reductase (DHFR)
This work was initiated by a collaboration with the team DUALS of UMR 6026 which found experimental evidence that osmolytes were able to modulate the catalytic rate of various enzyme. We choose to study the influence of osmolytes on DHFR. This enzyme has been extensively studied by NMR because it is a small protein produced in high quantity. The main conclusions are that osmolytes do not modify the overall structure of the enzyme and that the rate control is associated with the dissociation rate constant of substrate analog. No major variation of the protein dynamic in the rapid timescale was observed and the rate control is currently associated with the motion of the M20 loop which controls the product escape. Experiments of relaxation dispersion involving ms timescale protein motion are under progress and will permit to definitively explain the osmolyte mechanism on this enzyme (Legrand et al , in preparation).