1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics
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Catalysis-dependent selenium incorporation and migration in the nitrogenase active site iron-molybdenum cofactor

  1. Thomas Spatzal
  2. Kathryn A Perez
  3. James B Howard
  4. Douglas C Rees  Is a corresponding author
  1. Howard Hughes Medical Institute, California Institute of Technology, United States
  2. California Institute of Technology, United States
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Cite this article as: eLife 2015;4:e11620 doi: 10.7554/eLife.11620

Abstract

Dinitrogen reduction in the biological nitrogen cycle is catalyzed by nitrogenase, a two-component metalloenzyme. Understanding of the transformation of the inert resting state of the active site FeMo-cofactor into an activated state capable of reducing dinitrogen remains elusive. Here we report the catalysis dependent, site-selective incorporation of selenium into the FeMo-cofactor from selenocyanate as a newly identified substrate and inhibitor. The 1.60 Å resolution structure reveals selenium occupying the S2B site of FeMo-cofactor in the Azotobacter vinelandii MoFe-protein, a position that was recently identified as the CO-binding site. The Se2B-labeled enzyme retains substrate reduction activity and marks the starting point for a crystallographic pulse-chase experiment of the active site during turnover. Through a series of crystal structures obtained at resolutions of 1.32-1.66 Å, including the CO-inhibited form of Av1-Se2B, the exchangeability of all three belt-sulfur sites is demonstrated, providing direct insights into unforeseen rearrangements of the metal center during catalysis.

Article and author information

Author details

  1. Thomas Spatzal

    Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Kathryn A Perez

    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. James B Howard

    Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Douglas C Rees

    Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States
    For correspondence
    dcrees@caltech.edu
    Competing interests
    The authors declare that no competing interests exist.

Reviewing Editor

  1. Wilfred A van der Donk, University of Illinois at Urbana-Champaign, United States

Publication history

  1. Received: September 15, 2015
  2. Accepted: December 15, 2015
  3. Accepted Manuscript published: December 16, 2015 (version 1)
  4. Version of Record published: February 3, 2016 (version 2)

Copyright

© 2015, Spatzal et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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