Author: ["E. Joel Loveridge","Enas M. Behiry","Jiannan Guo","Rudolf K. Allemann"]
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Abstract
The question of whether protein motions play a role in the chemical step of enzymatic catalysis has generated much controversy in recent years. Debate has recently reignited over possible dynamic contributions to catalysis in dihydrofolate reductase, following conflicting conclusions from studies of the N23PP/S148A variant of the Escherichia coli enzyme. By investigating the temperature dependence of kinetic isotope effects, we present evidence that the reduction in the hydride transfer rate constants in this variant is not a direct result of impairment of conformational fluctuations. Instead, the conformational state of the enzyme immediately before hydride transfer, which determines the electrostatic environment of the active site, affects the rate constant for the reaction. Although protein motions are clearly important for binding and release of substrates and products, there appears to be no detectable dynamic coupling of protein motions to the hydride transfer step itself. The connection between protein dynamics and catalysis is an issue of vigorous debate in enzymology. Conformational motions are known to be important for the physical steps in the catalytic cycle of dihydrofolate reductase, however, it is now reported that there is no evidence of a correlation between such motions and the actual chemical step, hydride transfer. Cite this article
Loveridge, E., Behiry, E., Guo, J. et al. Evidence that a ‘dynamic knockout’ in Escherichia coli dihydrofolate reductase does not affect the chemical step of catalysis. Nature Chem 4, 292–297 (2012). https://doi.org/10.1038/nchem.1296 