Extended Data Fig. 3: Structural characterization of SnPolE and functional analysis of its substrate-coordination sites.
From: A two-metalloenzyme cascade constructs the azetidine-containing pharmacophore
a, Surface representation of SnPolE with Fe (orange sphere), BH4 (purple stick), and l-isoleucine (blue stick). b, The structure alignment of apo SnPolE (pink cartoon), SnPolE-BH4 (yellow cartoon), and SnPolE-BH4-l-isoleucine (green cartoon). c, Electron map of apo SnPolE. The 2Fo − Fc map is shown for Fe-coordinating residues and water (grey mesh, contoured at 1.0σ). Fe-coordinating residues are shown in lines and sticks, Fe is illustrated as orange sphere, and water is indicated as red sphere. d, Electron map of ligands bond in SnPolE-BH4 binary complex. The 2Fo − Fc map is shown for Fe-coordinating residues, water, and BH4 (grey mesh, contoured at 1.0σ). BH4 is shown in purple stick. e, Electron map of ligands bound in the SnPolE-BH4-l-isoleucine ternary complex structure. The Fo − Fc omit maps of l-isoleucine (cyan stick), Fe ions (orange spheres), the Fe-coordinating water molecule (red sphere) and Fe-coordinating residues (sticks) are contoured at 2.5σ (green mesh). f, Comparison of the binding pockets of apo SnPolE, SnPolE-BH4 binary complex, and SnPolE-BH4-l-isoleucine ternary complex. SnPolE, SnPolE-BH4, SnPolE-BH4-l-isoleucine is correspondingly shown in pink, yellow, and green. g, Crystal structure of SnPolEY157A variant with l-isoleucine mistakenly coordinated to iron. The selected amino acid residues and l-isoleucine are shown in the stick and ball, and Fe is illustrated as sphere. h, Comparison of active sites of SnPolEY157A (yellow) and SnPolE (white). i, Comparison of active sites of SnPolEF140A (deep teal) and SnPolE (white). j, Comparison of active sites of SnPolEY280A (pink) and SnPolE (white).
