The role of enzyme dynamics and tunnelling in catalysing hydride transfer: Studies of distal mutants of dihydrofolate reductase

Lin Wang, Nina M. Goodey, Stephen J. Benkovic, Amnon Kohen

Research output: Contribution to journalArticle

53 Scopus citations


Residues M42 and G121 of Escherichia coli dihydrofolate reductase (ecDHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ecDHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), their temperature dependence and activation parameters were studied. The findings presented here are in accordance with the environmentally coupled hydrogen tunnelling. In contrast to the wild-type (WT), fluctuations of the donor-acceptor distance were required, leading to a significant temperature dependence of KIEs and deflated intercepts. A comparison of M42W and G121V to the WT enzyme revealed that the reduced rates, the inflated primary KIEs and their temperature dependences resulted from an imperfect potential surface prearrangement relative to the WT enzyme. Apparently, the coupling of the enzyme's dynamics to the reaction coordinate was altered by the mutation, supporting the models in which dynamics of the whole protein is coupled to its catalysed chemistry.

Original languageEnglish
Pages (from-to)1307-1315
Number of pages9
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1472
StatePublished - 29 Aug 2006



  • Dihydrofolate reductase
  • Distal mutation
  • Enzyme dynamics
  • Hydrogen tunnelling
  • Kinetic isotope effect
  • Structure-dynamics-function relationship

Cite this