The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

Schrapers, Peer; Mebs, Stefan; Ilina, Yulia; Warner, D S; Wörmann, C; Schuth, Nils; Kositzki, Ramona; Dau, Holger; Limberg, Christian; Dobbek, Holger; Haumann, Michael

doi:10.1088/1742-6596/712/1/012029

Cited by 2 publications

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References 13 publications

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“…Similar edge spectra of oxidized and reduced samples and comparable shape changes in the CO/Me proteins suggested a largely analogous nickel coordination and similar effects of the treatments in the full-length and truncated variants. The low primary edge maximum and shallow edge slope of all spectra indicated preferential sulfur binding to nickel in low coordination environments [ 30 , 35 , 37 , 38 ] as found in the crystal structures [ 15 – 17 ]. The mean edge energy (~8341.2 eV) and the edge shoulder (~8338 eV) of the oxidized proteins suggested the predominant presence of square-planar (low-spin) Ni(II) species [ 30 , 39 ].…”

Section: Resultsmentioning

confidence: 94%

Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy

et al. 2017

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Bacteria integrate CO2 reduction and acetyl coenzyme-A (CoA) synthesis in the Wood-Ljungdal pathway. The acetyl-CoA synthase (ACS) active site is a [4Fe4S]-[NiNi] complex (A-cluster). The dinickel site structure (with proximal, p, and distal, d, ions) was studied by X-ray absorption spectroscopy in ACS variants comprising all three protein domains or only the C-terminal domain with the A-cluster. Both variants showed two square-planar Ni(II) sites and an OH- bound at Ni(II)p in oxidized enzyme and a H2O at Ni(I)p in reduced enzyme; a Ni(I)p-CO species was induced by CO incubation and a Ni(II)-CH3- species with an additional water ligand by a methyl group donor. These findings render a direct effect of the N-terminal and middle domains on the A-cluster structure unlikely.

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Section: Resultsmentioning

confidence: 94%

Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy

et al. 2017

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“…More importantly, the study does not show a significant change in the near-edge, pre-edge, or Fourier transforms upon CO treatment, indicating that an insignificant amount of the Ni–CO species was present in the sample. A more recent conference proceeding 69 shows low-resolution Ni K-edge EXAFS data ( k ~ 12 Å −1 ) on partially loaded as-isolated and reduced ACS, which are quantitatively different from those of Cramer et al 59 To complicate the analysis further, an EXAFS study of ACS containing Cu at the proximal center (i.e., Cu p Ni d ) shows a dramatically short Cu–Ni distance (2.67 Å) compared to the longer Ni–Ni distance observed in other studies (~2.9 Å). 37 These earlier Ni K-edge and EXAFS investigations performed on ACS have all yielded incorrect and at best incomplete information about the active site of ACS.…”

Section: Resultsmentioning

confidence: 99%

X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase

et al. 2017

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Acetyl-CoA synthase (ACS) is a key enzyme in the Wood–Ljungdahl pathway of anaerobic CO2 fixation, which has long been proposed to operate by a novel mechanism involving a series of protein-bound organometallic (Ni–CO, methyl–Ni, and acetyl–Ni) intermediates. Here we report the first direct structural evidence of the proposed metal–carbon bond. We describe the preparation of the highly active metal-replete enzyme and near-quantitative generation of the kinetically competent carbonylated intermediate. This advance has allowed a combination of Ni and Fe K-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure experiments along with density functional theory calculations. The data reveal that CO binds to the proximal Ni of the six-metal metallocenter at the active site and undergoes dramatic structural and electronic perturbation in forming this organometallic Ni–CO intermediate. This direct identification of a Ni–carbon bond in the catalytically competent CO-bound form of the A cluster of ACS provides definitive experimental structural evidence supporting the proposed organometallic mechanism of anaerobic acetyl-CoA synthesis.

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The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

Cited by 2 publications

References 13 publications

Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy

Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy

X-ray Absorption Spectroscopy Reveals an Organometallic Ni–C Bond in the CO-Treated Form of Acetyl-CoA Synthase

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