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. Author manuscript; available in PMC: 2019 Nov 28.
Published in final edited form as: Chem Rev. 2018 Oct 29;118(22):10840–11022. doi: 10.1021/acs.chemrev.8b00074

Figure 57.

Figure 57.

(A) Reduced active site of CcO featuring the tris-His ligation for CuB; the overall geometry is distorted T- or Y-shaped, and for H290 and H291, binding occurs to the Nε atom of the imidazole groups. (B) A PHM derivative in the oxidized state. Here, CuH is also found in a distorted T-shaped geometry, where H107 and H108 form a near-linear coordination environment (∠ H107-Cu-H108 = 164°). By contrast, these two His residues bind the copper ion through their imidazole Nδ atoms in a very favorable strong binding interaction (as does H172). See text for further discussion.