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Figure 3
Hemichrome sites shown for different DHP-B structures. (a) Neutron crystallography structure (NX). (b) Serial femtosecond crystallography structure (SFX). (c) Serial synchrotron structure (SSX). (d) Superposition of the fully occupied hemichrome found in the neutron structure (orange) with the nonhemichrome heme site from the SFX structure (blue). Note the heme shift towards the enzyme surface upon the formation of the hemichrome, as well as the conformational changes of the ligating His residues. Relevant coordination bonds between the heme iron and the proximal and distal histidine ligands, including those involved in the hemichrome species, are shown as black dashed lines. All electron-density (2Fo – Fc) maps are shown as a blue mesh and contoured at 1σ. Difference density (Fo – Fc) maps are shown as a green or red mesh for positive or negative differences, respectively, and are contoured at 3σ.

IUCrJ
Volume 9| Part 5| September 2022| Pages 610-624
ISSN: 2052-2525
https://doi.org/10.1107/S2052252522006418