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Metal-Ligand Bonds

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Updated: Jul 15, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

EPR characterization of a metal-binding site in RquA.

Rachelle K Stowell1, Trilok Neupane2, Kristian C Mankiller3

  • 1Department of Chemistry, University of Washington, Seattle, WA, USA.

Journal of Biological Inorganic Chemistry : JBIC : a Publication of the Society of Biological Inorganic Chemistry
|July 14, 2026
PubMed
Summary

Rhodoquinone biosynthesis enzyme (RquA) requires divalent metal cations for activity. This study reveals Mn(II) and Co(II) bind RquA with high affinity, elucidating a potential metal binding site crucial for anaerobic metabolism.

Keywords:
S-adenosyl-L-methionineEPRHYSCOREICP-MSITCRquAmanganese

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Last Updated: Jul 15, 2026

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11:19

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Published on: July 4, 2016

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Rhodoquinone (RQ) is vital for anaerobic metabolism in various organisms.
  • Rhodoquinone biosynthesis enzyme (RquA) catalyzes ubiquinone (UQ) to RQ conversion using S-adenosyl-L-methionine.
  • RquA activity is enhanced by divalent metal cations.

Purpose of the Study:

  • To investigate the metal dependence of RquA activity.
  • To characterize the interaction of RquA with Mn(II), Co(II), and Zn(II).
  • To elucidate the structural basis of RquA function through metal binding site identification.

Main Methods:

  • Enzyme activity assays in the presence of divalent metal cations.
  • Spectroscopic studies using Electron Paramagnetic Resonance (EPR) with Mn(II) as a probe.
  • Pulse EPR experiments on natural-abundance and 15N-labeled RquA.
  • Integration of experimental data with AlphaFold3-derived structural models.

Main Results:

  • Mn(II) and Co(II) bind RquA with sub-micromolar affinities and 1:1 stoichiometry.
  • EPR spectroscopy identified a specific Mn(II) binding site with distinct spectroscopic parameters.
  • Pulse EPR revealed a weakly-to-moderately coupled nitrogen ligand interacting with the metal ion.
  • A putative metal binding site was proposed based on integrated experimental and structural data.

Conclusions:

  • Divalent metal cations, particularly Mn(II) and Co(II), are essential for RquA function.
  • The study provides detailed spectroscopic insights into the RquA metal binding site.
  • This work offers a structural basis for understanding RquA's role in rhodoquinone biosynthesis and anaerobic metabolism.