Extended Data Figure 4 ∣. Peripheral 5His coordination site of 2Co^II-(AB)₂ and rotamer analysis of the H100 side chain.

a, Co^II-coordination in the dimer interface of (AB)₂ with the 2mF_o-DF_c electron density map (grey mesh) contoured at 5.0 σ (metal) and 1.5 σ (ligand). Coordination distances and angles between Co^II and ligands are shown on the right. b, Possible rotamer orientations of H100 residue in the crystal structure of 2Ni^II-(AB)₂. Rotamers were generated with the combination of χ₁ (torsion angle of C_α-C_β = 60–300°, 60° interval) and χ₂ (torsion angle of C_β-C_γ = 0–330°, 30° interval). c, Averaged number of atomic contacts of H100 rotamers as a function of van der waals (VdW) overlap. Error bars reflect the standard deviations of the atomic contacts in rotamers with fixed χ₁ and variable χ₂. Compared to the original conformation of H100, all possible rotamers show significant clashes with proximal residues. d, Location of proximal residues overlapped with H100 rotamers.