Structural evolution of nitrogenase states under alkaline turnover

Abstract Biological nitrogen fixation, performed by the enzyme nitrogenase, supplies nearly 50% of the bioavailable nitrogen pool on Earth, yet the structural nature of the enzyme intermediates involved in this cycle remains ambiguous. Here we present four high resolution cryoEM structures of the ni...

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Main Authors: Rebeccah A. Warmack, Douglas C. Rees
Format: Article
Language:English
Published: Nature Portfolio 2024-12-01
Series:Nature Communications
Online Access:https://doi.org/10.1038/s41467-024-54713-0
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author Rebeccah A. Warmack
Douglas C. Rees
author_facet Rebeccah A. Warmack
Douglas C. Rees
author_sort Rebeccah A. Warmack
collection DOAJ
description Abstract Biological nitrogen fixation, performed by the enzyme nitrogenase, supplies nearly 50% of the bioavailable nitrogen pool on Earth, yet the structural nature of the enzyme intermediates involved in this cycle remains ambiguous. Here we present four high resolution cryoEM structures of the nitrogenase MoFe-protein, sampled along a time course of alkaline reaction mixtures under an acetylene atmosphere. This series of structures reveals a sequence of salient changes including perturbations to the inorganic framework of the FeMo-cofactor; depletion of the homocitrate moiety; diminished density around the S2B belt sulfur of the FeMo-cofactor; rearrangements of cluster-adjacent side chains; and the asymmetric displacement of the FeMo-cofactor. We further demonstrate that the nitrogenase associated factor T protein can recognize and bind an alkaline inactivated MoFe-protein in vitro. These time-resolved structures provide experimental support for the displacement of S2B and distortions of the FeMo-cofactor at the E0-E3 intermediates of the substrate reduction mechanism, prior to nitrogen binding, highlighting cluster rearrangements potentially relevant to nitrogen fixation by biological and synthetic clusters.
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spelling doaj-art-ac48b35a775445708fca8e3d216a3ea52025-08-20T03:40:50ZengNature PortfolioNature Communications2041-17232024-12-0115111210.1038/s41467-024-54713-0Structural evolution of nitrogenase states under alkaline turnoverRebeccah A. Warmack0Douglas C. Rees1Division of Chemistry and Chemical Engineering 147-75 California Institute of TechnologyDivision of Chemistry and Chemical Engineering 147-75 California Institute of TechnologyAbstract Biological nitrogen fixation, performed by the enzyme nitrogenase, supplies nearly 50% of the bioavailable nitrogen pool on Earth, yet the structural nature of the enzyme intermediates involved in this cycle remains ambiguous. Here we present four high resolution cryoEM structures of the nitrogenase MoFe-protein, sampled along a time course of alkaline reaction mixtures under an acetylene atmosphere. This series of structures reveals a sequence of salient changes including perturbations to the inorganic framework of the FeMo-cofactor; depletion of the homocitrate moiety; diminished density around the S2B belt sulfur of the FeMo-cofactor; rearrangements of cluster-adjacent side chains; and the asymmetric displacement of the FeMo-cofactor. We further demonstrate that the nitrogenase associated factor T protein can recognize and bind an alkaline inactivated MoFe-protein in vitro. These time-resolved structures provide experimental support for the displacement of S2B and distortions of the FeMo-cofactor at the E0-E3 intermediates of the substrate reduction mechanism, prior to nitrogen binding, highlighting cluster rearrangements potentially relevant to nitrogen fixation by biological and synthetic clusters.https://doi.org/10.1038/s41467-024-54713-0
spellingShingle Rebeccah A. Warmack
Douglas C. Rees
Structural evolution of nitrogenase states under alkaline turnover
Nature Communications
title Structural evolution of nitrogenase states under alkaline turnover
title_full Structural evolution of nitrogenase states under alkaline turnover
title_fullStr Structural evolution of nitrogenase states under alkaline turnover
title_full_unstemmed Structural evolution of nitrogenase states under alkaline turnover
title_short Structural evolution of nitrogenase states under alkaline turnover
title_sort structural evolution of nitrogenase states under alkaline turnover
url https://doi.org/10.1038/s41467-024-54713-0
work_keys_str_mv AT rebeccahawarmack structuralevolutionofnitrogenasestatesunderalkalineturnover
AT douglascrees structuralevolutionofnitrogenasestatesunderalkalineturnover