Effect of Asp122 Mutation on the Hydride Transfer in E. coli DHFR Demonstrates the Goldilocks of Enzyme Flexibility

Anil R. Mhashal, Yaron Pshetitsky, Reuven Eitan, Christopher M. Cheatum, Amnon Kohen, Dan Thomas Major

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF) in the presence of NADPH. The key hydride transfer step in the reaction is facilitated by a combination of enzyme active site preorganization and correlated protein motions in the Michaelis-Menten (E:NADPH:DHF) complex. The present theoretical study employs mutagenesis to examine the relation between structural and functional properties of the enzyme. We mutate Asp122 in Escherichia coli DHFR, which is a conserved amino acid in the DHFR family. The consequent effect of the mutation on enzyme catalysis is examined from an energetic, structural and short-Time dynamic perspective. Our investigations suggest that the structural and short-Time dynamic perturbations caused by Asp122X mutations (X = Asn, Ser, Ala) are along the reaction coordinate and lower the rate of hydride transfer. Importantly, analysis of the correlated and principle component motions in the enzyme suggest that the mutation alters the coupled motions that are present in the wild-Type enzyme. In the case of D122N and D122S, the mutations inhibit coupled motion, whereas in the case of D122A, the mutation enhances coupled motion, although all mutations result in similar rate reduction. These results emphasize a Goldilocks principle of enzyme flexibility, that is, enzymes should neither be too rigid nor too flexible.

Original languageEnglish
Pages (from-to)8006-8017
Number of pages12
JournalJournal of Physical Chemistry B
Issue number33
StatePublished - 23 Aug 2018

Bibliographical note

Funding Information:
This work was supported by Israel Science Foundation Grant 2146/15 and United States−Israel Binational Science Foundation Grant 2012340.

Publisher Copyright:
Copyright © 2018 American Chemical Society.


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