Titill: | Quantum Mechanics/Molecular Mechanics Study of Resting-State Vanadium Nitrogenase: Molecular and Electronic Structure of the Iron–Vanadium Cofactor |
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Útgáfa: | 2020-08-05 |
Tungumál: | Enska |
Umfang: | 11514-11527 |
Háskóli/Stofnun: | Háskóli Íslands University of Iceland |
Svið: | Verkfræði- og náttúruvísindasvið (HÍ) School of Engineering and Natural Sciences (UI) |
Deild: | Raunvísindastofnun (HÍ) Science Institute (UI) |
Birtist í: | Inorganic Chemistry;59(16) |
ISSN: | 0020-1669 1520-510X (eISSN) |
DOI: | 10.1021/acs.inorgchem.0c01320 |
Efnisorð: | FeMo cofactor; X-rays; Ligands; QM/MM; Crystal structure; Skammtafræði |
URI: | https://hdl.handle.net/20.500.11815/2235 |
Tilvitnun:Benediktsson, B. and R. Bjornsson (2020). "Quantum Mechanics/Molecular Mechanics Study of Resting-State Vanadium Nitrogenase: Molecular and Electronic Structure of the Iron–Vanadium Cofactor." Inorganic Chemistry 59(16): 11514-11527.
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Útdráttur:The nitrogenase enzymes are responsible for all biological nitrogen reduction. How this is accomplished at the atomic level, however, has still not been established. The molybdenum-dependent nitrogenase has been extensively studied and is the most active catalyst for dinitrogen reduction of the nitrogenase enzymes. The vanadium-dependent form, on the other hand, displays different reactivity, being capable of CO and CO2 reduction to hydrocarbons. Only recently did a crystal structure of the VFe protein of vanadium nitrogenase become available, paving the way for detailed theoretical studies of the iron-vanadium cofactor (FeVco) within the protein matrix. The crystal structure revealed a bridging 4-atom ligand between two Fe atoms, proposed to be either a CO32- or NO3- ligand. Using a quantum mechanics/molecular mechanics model of the VFe protein, starting from the 1.35 Å crystal structure, we have systematically explored multiple computational models for FeVco, considering either a CO32- or NO3- ligand, three different redox states, and multiple broken-symmetry states. We find that only a [VFe7S8C(CO3)]2- model for FeVco reproduces the crystal structure of FeVco well, as seen in a comparison of the Fe-Fe and V-Fe distances in the computed models. Furthermore, a broken-symmetry solution with Fe2, Fe3, and Fe5 spin-down (BS7-235) is energetically preferred. The electronic structure of the [VFe7S8C(CO3)]2- BS7-235 model is compared to our [MoFe7S9C]- BS7-235 model of FeMoco via localized orbital analysis and is discussed in terms of local oxidation states and different degrees of delocalization. As previously found from Fe X-ray absorption spectroscopy studies, the Fe part of FeVco is reduced compared to FeMoco, and the calculations reveal Fe5 as locally ferrous. This suggests resting-state FeVco to be analogous to an unprotonated E1 state of FeMoco. Furthermore, V-Fe interactions in FeVco are not as strong compared to Mo-Fe interactions in FeMoco. These clear differences in the electronic structures of otherwise similar cofactors suggest an explanation for distinct differences in reactivity.
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Athugasemdir:Publisher's version (útgefin grein)
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Leyfi:This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
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