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New Crystallographic Snapshots of Large Domain Movements in Bacterial 3‑Hydroxy-3-methylglutaryl Coenzyme A Reductase
journal contribution
posted on 2018-09-10, 00:00 authored by Edwin
R. Ragwan, Eri Arai, Yan KungThe
enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase
(HMGR) catalyzes the first committed step of the mevalonate pathway,
which is used across biology in the biosynthesis of countless metabolites.
HMGR consumes 2 equiv of the cofactor NAD(P)H to perform the four-electron
reduction of HMG-CoA to mevalonate toward the production of steroids
and isoprenoids, the largest class of natural products. Recent structural
data have shown that HMGR contains a highly mobile C-terminal domain
(CTD) that is believed to adopt many different conformations to permit
binding and dissociation of the substrate, cofactors, and products
at specific points during the reaction cycle. Here, we have characterized
the HMGR from Delftia acidovorans as an NADH-specific
enzyme and determined crystal structures of the enzyme in unbound,
mevalonate-bound, and NADH- and citrate-bound states. Together, these
structures depict ligand binding in both the active site and the cofactor-binding
site while illustrating how a conserved helical motif confers NAD(P)H
cofactor specificity. Unexpectedly, the NADH-bound structure also
reveals a new conformation of the CTD, in which the domain has “flipped”
upside-down, while directly binding the cofactor. By capturing these
structural snapshots, this work not only expands the known range of
HMGR domain movement but also provides valuable insight into the catalytic
mechanism of this biologically important enzyme.
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Keywords
four-electron reductionreaction cycleHMGR domain movementC-terminal domaincitrate-bound statesligand bindingconformationDelftia acidovoransenzyme 3- hydroxy -3-methylglutaryl coenzymecofactor-binding siteLarge Domain MovementsCTD2 equivNADH-specific enzymehelical motifcrystal structuresNADH-bound structuremevalonate pathwayHMG-CoA
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