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. 2021 May 18;296:100795. doi: 10.1016/j.jbc.2021.100795

Figure 4.

Figure 4

The Arg cage.A, superimposition between the structures of wildtype E. coli pyridoxine 5’-phosphate oxidase (gold) (Protein Data Bank code: 1G79) and pyridoxal 5’-phosphate (PLP)-bound ePNPOqm (gray), and blow-up showing the Fo–Fc omit maps (green for PLP, contained in PLP-ePNPOqm, and red for phosphate, contained in the 1G79 structure). By contouring at 2.5 σ, a significant difference in steric hindrance is visible, revealing the presence of a bulkier ligand with respect to a phosphate ion. The side chains of arginine residues lining the cage are represented as sticks. B, superimposition between the structures of ePNPOqm in the free (green) and PLP-bound (gray) forms and blow-up showing that PLP is seized in the superficial cleft mainly via electrostatic interactions, mediated by three arginine residues. A water molecule (red sphere) bridges Arg23 and the PLP phosphate group through a hydrogen bonds network. PLP and the side chains of arginine residues lining the cage are represented as sticks.