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. Author manuscript; available in PMC: 2015 Sep 26.
Published in final edited form as: Science. 2014 Sep 26;345(6204):1620–1623. doi: 10.1126/science.1256679

Figure 1. CO-inhibited MoFe-protein (Av1-CO).

Figure 1

Refined structure of the CO-bound FeMo-cofactor at a resolution of 1.50 Å. A) View along the Fe1-C-Mo direction. The electron density (2Fo-Fc) map is contoured at 4.0 σ and represented as blue mesh. The density at the former S2B site is significantly decreased and in excellent agreement with bound CO (see also C)). B) Same orientation as A) superimposed with the anomalous density map calculated at 7100 eV (green) at a resolution of 2.1 Å contoured at 4.0 σ showing the significant reduction of anomalous electron density at the CO site. C) Side view of FeMo-cofactor highlighting the μ2 binding geometry of CO. The electron density (2Fo-Fc) map (blue mesh) surrounding CO-Fe2-Fe6-C is contoured at 1.5 σ. D) Same orientation as C) highlighting the ligand environment of the metal center. The catalytically important side chain residues α-Val70 and α-His195 are in close proximity to the CO-binding site. Iron atoms are shown in orange, sulfur in yellow, molybdenum in turquoise, carbon in grey, nitrogen in blue and oxygen in red.