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Modeling the Role of a Flexible Loop and Active Site Side Chains in Hydride Transfer Catalyzed by Glycerol-3-Phosphate Dehydrogenase

preprint
submitted on 23.06.2020 and posted on 25.06.2020 by Anil Ranu Mhashal, Adrian Romero-Rivera, Lisa S. Mydy, Judith R. Cristobal, Andrew M. Gulick, John Richard, Shina Caroline Lynn Kamerlin

Glycerol-3-phosphate dehydrogenase is a biomedically important enzyme that plays a crucial role in lipid biosynthesis. It is activated by a ligand-gated conformational change that is necessary for the enzyme to reach a catalytically competent conformation capable of efficient transition state stabilization. While the human form (hlGPDH) has been the subject of extensive structural and biochemical studies, corresponding computational studies to support and extend the experimental observations have been lacking. We perform here detailed empirical valence bond and Hamiltonian replica exchange molecular dynamics simulations of wild-type hlGPDH and its variants, as well as providing a novel crystal structure of the binary hlGPDH·NAD R269A variant where the enzyme is present in the open conformation. We estimated the activation free energies for the hydride transfer reaction in wild-type and substituted variants of hlGPDH and investigated the effect of mutations on the catalysis from a detailed structural study. Our structural data and simulations also illustrate the critical role of the R269 side chain in facilitating the closure of hlGPDH into a catalytically competent conformation, through modulating the flexibility of a key catalytic loop (292-LNGQKL-297), thus rationalizing a tremendous 41,000-fold decrease experimentally in the turnover number, kcat, upon truncating this residue. Taken together, our data highlight the importance of this ligand-gated conformational change in catalysis, a feature that can be exploited both for protein engineering and for the design of novel allosteric inhibitors targeting this biomedically important enzyme.

Funding

Swedish Research Council

Human Frontier Science Program

Natural Sciences and Engineering Research Council

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Knut and Alice Wallenberg Foundation

NATIONAL INSTITUTES OF HEALTH (NIH)

United States Department of Health and Human Services

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National Cancer Institute

National Institute of General Medical Sciences (NIGMS)

United States Department of Health and Human Services

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SNIC 2.0: Swedish National Infrastructure for Computing

Swedish Research Council

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History

Email Address of Submitting Author

lynn.kamerlin@kemi.uu.se

Institution

Uppsala University

Country

Sweden

ORCID For Submitting Author

0000-0002-3190-1173

Declaration of Conflict of Interest

No conflict of interest.

Version Notes

Version 1.0 / initial submission.

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