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Structure of precursor-bound NifEN: a nitrogenase FeMo cofactor maturase/insertase.

ABSTRACT: NifEN plays an essential role in the biosynthesis of the nitrogenase iron-molybdenum (FeMo) cofactor (M cluster). It is an ?(2)?(2) tetramer that is homologous to the catalytic molybdenum-iron (MoFe) protein (NifDK) component of nitrogenase. NifEN serves as a scaffold for the conversion of an iron-only precursor to a matured form of the M cluster before delivering the latter to its target location within NifDK. Here, we present the structure of the precursor-bound NifEN of Azotobacter vinelandii at 2.6 angstrom resolution. From a structural comparison of NifEN with des-M-cluster NifDK and holo NifDK, we propose similar pathways of cluster insertion for the homologous NifEN and NifDK proteins.

SUBMITTER: Kaiser JT

PROVIDER: S-EPMC3138709 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Structure of precursor-bound NifEN: a nitrogenase FeMo cofactor maturase/insertase.

Kaiser Jens T JT Hu Yilin Y Wiig Jared A JA Rees Douglas C DC Ribbe Markus W MW

Science (New York, N.Y.) 20110101 6013

NifEN plays an essential role in the biosynthesis of the nitrogenase iron-molybdenum (FeMo) cofactor (M cluster). It is an α(2)β(2) tetramer that is homologous to the catalytic molybdenum-iron (MoFe) protein (NifDK) component of nitrogenase. NifEN serves as a scaffold for the conversion of an iron-only precursor to a matured form of the M cluster before delivering the latter to its target location within NifDK. Here, we present the structure of the precursor-bound NifEN of Azotobacter vinelandii ...[more]

PMID: 21212358

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Ligand-bound S = 1/2 FeMo-cofactor of nitrogenase: hyperfine interaction analysis and implication for the central ligand X identity.

Project description:Broken symmetry density functional theory (BS-DFT) has been used to address the hyperfine parameters of the single atom ligand X, proposed to be coordinated by six iron ions in the center of the paramagnetic FeMo-cofactor (FeMoco) of nitrogenase. Using the X = N alternative, we recently found that any hyperfine signal from X would be small (calculated A(iso)(X = (14)N) = 0.3 MHz) due to both structural and electronic symmetry properties of the [Mo-7Fe-9S- X] FeMoco core in its resting S = 3/2 state. Here, we extend our BS-DFT approach to the 2e(-) reduced S = 1/2 FeMoco state. Alternative substrates coordinated to this FeMoco state effectively perturb the electronic and/or structural symmetry properties of the cofactor. Using an example of an allyl alcohol (H2C=CH-CH2-OH) product ligand, we consider three different binding modes at single iron site and three different BS-DFT spin state structures and show that this binding would enhance the key hyperfine signal A(iso)(X) by at least 1 order of magnitude (3.8 < or = A(iso)(X = (14)N) < or = 14.7 MHz), and this result should not depend strongly on the exact identity of X (nitrogen, carbon, or oxygen). The interstitial atom, when the nucleus has a nonzero magnetic moment, should therefore be observable by ESR methods for some ligand-bound FeMoco states. In addition, our results illustrate structural details and likely spin-coupling patterns for models for early intermediates in the catalytic cycle.

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On reversible H2 loss upon N2 binding to FeMo-cofactor of nitrogenase.

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