title: Use of transferred nuclear Overhauser effect measurements to compare binding of coenzyme analogues to dihydrofolate reductase.
abstract: Transferred nuclear Overhauser effect measurements have been made on complexes of NADP+ and thioNADP+ with Lactobacillus casei dihydrofolate reductase to provide information about the glycosidic bond conformations in these complexes. Both NADP+ and thioNADP+ are shown to have very similar anti conformations about their adenine glycosidic bonds when bound to the enzyme. However, their nicotinamide glycosidic bond conformations are very different: while NADP+ binds in an exclusively anti conformation, thioNADP+ binds with a distribution of syn/anti conformations very similar to that observed in nicotinamide mononucleotides in free solution (approximately 50:50). Thus for thioNADP+, binding to the enzyme does not significantly perturb the potential function for rotation about the nicotinamide glycosidic bond. Earlier NMR studies [Hyde, E. I., Birdsall, B., Roberts, G. C. K., Feeney, J., & Burgen, A. S. V. (1980) Biochemistry 19, 3738] had indicated that large downfield 1H shifts of the nicotinamide ring protons (0.61-1.36 ppm) are detected on binding NADP+ while only very small shifts (less than 0.1 ppm) are observed in complexes with thioNADP+. The chemical shift and conformational findings are best explained if the thionicotinamide ring extends into solution making essentially no contacts with the enzyme.
mesh_terms: D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D007780:Lacticaseibacillus casei / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009249:NADP / Q000031:analogs & derivatives; D009536:Niacinamide; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism*
chemical_list: C015541:thionicotinamide adenine dinucleotide phosphate; D009536:Niacinamide; D009249:NADP; D013762:Tetrahydrofolate Dehydrogenase