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Figure 5
Differences in H-atom positions. (a) Electron density of H atoms around His148 and Tyr66 in T203I. (b) Electron density of H atoms around His148 and Tyr66 in S65T. (c) Electron density of H atoms around Glu222 and Ser65 in T203I. (d) Electron density of H atoms around Glu222 and Thr65 in S65T. (e) Electron density of H atoms around Gln222 and Ser65 in E222Q. The 2Fo − Fc map for Wat3 contoured at 4σ and 6σ and the Fo − Fc OMIT map for H atoms contoured at 2σ and 3σ are shown in gray and pink, respectively. Hydrogen bonds are represented as broken lines. The distances between the donor and acceptor are listed in Supplementary Table S4. The minor conformations are shown as transparent models. (f) Electron density of H atoms and a minor conformation of Thr203 in S65T. Its occupancy is 0.08. (g) Electron density of H atoms and a minor conformation of Thr203 in E222Q. Its occupancy is 0.19. The Fo − Fc OMIT map for the minor conformations contoured at 4σ and 7σ is shown in beige. The Fo − Fc OMIT map for H atoms contoured at 1σ, 2σ and 3σ is shown in pink. (h) The structural difference between the A (T203I) and B (E222Q) forms. The gradient-colored arrows indicate the positional shift between the two forms. A hydrogen bond between Thr203 and His148 in the E222Q variant is shown as a red dotted line, with a donor–acceptor distance of 2.956 (9) Å.

IUCrJ
Volume 6| Part 3| May 2019| Pages 387-400
ISSN: 2052-2525
https://doi.org/10.1107/S205225251900246X