Interpretation of nuclear magnetic resonance spectra for Lactobacillus casei dihydrofolate reductase on the basis of the x-ray structure of the enzyme-methotrexate-NADPH complex

Abstract

The 3-dimensional molecular structure of L. casei dihydrofolate reductase complexed with NADPH and methotrexate was used to interpret published magnetic resonance spectra for this enzyme. Proton resonances from histidine residues and 19F resonances from fluorine-labeled fluorotyrosine and fluorotryptophan dihydrofolate reductase were assigned in several cases to specific amino acids in the primary sequence. The 31P signals from the pyrophosphate moiety of bound NADPH were assigned and the large upfield shift for 13C-labeled (at the carboxamide C) NADP+ upon binding to the reductase was explained in terms of desolvation effects.