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J Mol Biol. 2018 Sep 14;430(18 Pt B):3234-3250. doi: 10.1016/j.jmb.2018.06.015. Epub 2018 Jun 20.

Biliverdin Reductase B Dynamics Are Coupled to Coenzyme Binding.

Author information

1
Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA.
2
National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
3
Department of Chemistry & Biochemistry, Florida State University, Tallahassee, FL 32310, USA.
4
Division of Medical Oncology, School of Medicine, Aurora, CO 80045, USA.
5
Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA. Electronic address: Elan.Eisenmesser@ucdenver.edu.

Abstract

Biliverdin reductase B (BLVRB) is a newly identified cellular redox regulator that catalyzes the NADPH-dependent reduction of multiple substrates. Through mass spectrometry analysis, we identified high levels of BLVRB in mature red blood cells, highlighting the importance of BLVRB in redox regulation. The BLVRB conformational changes that occur during conezyme/substrate binding and the role of dynamics in BLVRB function, however, remain unknown. Through a combination of NMR, kinetics, and isothermal titration calorimetry studies, we determined that BLVRB binds its coenzyme 500-fold more tightly than its substrate. While the active site of apo BLVRB is highly dynamic on multiple timescales, active site dynamics are largely quenched within holo BLVRB, in which dynamics are redistributed to other regions of the enzyme. We show that a single point mutation of Arg78➔Ala leads to both an increase in active site micro-millisecond motions and an increase in the microscopic rate constants of coenzyme binding. This demonstrates that altering BLVRB active site dynamics can directly cause a change in functional characteristics. Our studies thus address the solution behavior of apo and holo BLVRB and identify a role of enzyme dynamics in coenzyme binding.

KEYWORDS:

coenzyme; dynamics; enzyme; network; nuclear magnetic resonance

PMID:
29932944
PMCID:
PMC6431292
DOI:
10.1016/j.jmb.2018.06.015
[Indexed for MEDLINE]
Free PMC Article

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