Spectroscopic Characterization of an Eight-Iron Nitrogenase Cofactor Precursor that Lacks the "9th Sulfur"

Andrew J Jasniewski; Jarett Wilcoxen; Kazuki Tanifuji; Britt Hedman; Keith O Hodgson; R David Britt; Yilin Hu; Markus W Ribbe

doi:10.1002/anie.201907593

Spectroscopic Characterization of an Eight-Iron Nitrogenase Cofactor Precursor that Lacks the "9^th Sulfur"

Angew Chem Int Ed Engl. 2019 Oct 7;58(41):14703-14707. doi: 10.1002/anie.201907593. Epub 2019 Sep 5.

Authors

Andrew J Jasniewski¹, Jarett Wilcoxen², Kazuki Tanifuji¹, Britt Hedman³, Keith O Hodgson^{3

4}, R David Britt², Yilin Hu¹, Markus W Ribbe^{1

5}

Affiliations

¹ Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA.
² Department of Chemistry, University of California, Davis, Davis, CA, 95616, USA.
³ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA.
⁴ Department of Chemistry, Stanford University, Stanford, CA, 94305, USA.
⁵ Department Chemistry, University of California, Irvine, Irvine, CA, 92697-2025, USA.

Abstract

Nitrogenases catalyze the reduction of N₂ to NH₄⁺ at its cofactor site. Designated the M-cluster, this [MoFe₇ S₉ C(R-homocitrate)] cofactor is synthesized via the transformation of a [Fe₄ S₄ ] cluster pair into an [Fe₈ S₉ C] precursor (designated the L-cluster) prior to insertion of Mo and homocitrate. We report the characterization of an eight-iron cofactor precursor (designated the L*-cluster), which is proposed to have the composition [Fe₈ S₈ C] and lack the "9^th sulfur" in the belt region of the L-cluster. Our X-ray absorption and electron spin echo envelope modulation (ESEEM) analyses strongly suggest that the L*-cluster represents a structural homologue to the l-cluster except for the missing belt sulfur. The absence of a belt sulfur from the L*-cluster may prove beneficial for labeling the catalytically important belt region, which could in turn facilitate investigations into the reaction mechanism of nitrogenases.

Keywords: NifB; bioinorganic chemistry; iron-sulfur clusters; metalloenzymes; nitrogenase.

Publication types

Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.
Review

MeSH terms

Coenzymes / chemistry*
Models, Molecular
Molecular Structure
Nitrogenase / chemistry
Nitrogenase / metabolism*
Spectrum Analysis / methods*
Sulfur / chemistry*
X-Ray Absorption Spectroscopy

Substances

Coenzymes
Sulfur
Nitrogenase

Abstract

Publication types

MeSH terms

Substances

Grants and funding