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Figure 6
Conformation of residues in the hydro­phobic proton cavity and T2Cu site of as-isolated, NO-soaked Phe295Leu, and the T2Cu site of Phe295Leu reduced RpNiR mutant structures. The interaction of residues at the entrance cavity is shown in (A) wtRpNiR (3ziy), (B) as-isolated Phe295Leu RpNiR with electron-density map and details of interactions, and (C) NO-soaked Phe295Leu RpNiR with electron-density map and details of interactions, revealing two alternative conformations of Leu295. The yellow dotted line indicates the closest distance between residues Phe295 and Val140. (D) Di­thio­nite-soaked Phe295Leu RpNiR with electron-density map. (E) Details of Tyr323 interactions in the bent conformation along with linker loop residues 317–322. (F) Alignment of three Tyr323 conformations, including locked down (3ziy), open (5ocf) and bent conformation, are shown in grey, green and magenta sticks, respectively. The 2Fo − Fc electron-density map is contoured at 1.0σ and shown as a grey mesh for as-isolated and NO-soaked RpNiR Phe295Leu structures and as a blue mesh for di­thio­nite-soaked Phe295Leu RpNiR. Phe295Leu RpNiR is shown in magenta and orange, and wtRpNiR in green and blue. Small red spheres represent water molecules, the black dashed lines are the hydrogen bonds, the red dashed lines are the interactions involving T2Cu and the deep blue sphere is T2Cu.

IUCrJ
Volume 13| Part 4| July 2026|
ISSN: 2052-2525
https://doi.org/10.1107/S2052252526004549