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Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures
Published on: December 1, 2020
Dose-dependent structural and electron-density features in the lytic polysaccharide monooxygenase NcAA9D
Samuel A Miller1,2, William B O'Dell1,2, Flora Meilleur1,2
1Department of Molecular and Structural Biochemistry, North Carolina State University, 128 Polk Hall, Raleigh, NC 27695, USA.
Acta Crystallographica. Section D, Structural Biology
|July 28, 2026
Summary
X-ray crystallography of copper-containing lytic polysaccharide monooxygenases (LPMOs) can be hindered by radiation damage. This study reveals how X-ray dose affects LPMO active sites, aiding accurate structural analysis of sensitive enzymes.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- X-ray crystallography is crucial for studying copper-containing lytic polysaccharide monooxygenases (LPMOs).
- Radiation damage during X-ray data collection can complicate structural analysis of LPMOs.
- Understanding radiation effects is vital for accurate structural determination of these enzymes.
Purpose of the Study:
- To investigate the progressive effects of X-ray radiation damage on the active site of NcAA9D, a Neurospora crassa AA9-family LPMO.
- To analyze the dose-dependence of active-site geometry and copper-bound species in LPMOs.
- To provide insights into the impact of X-ray dose on electron density and potential radiation-sensitive intermediates.
Main Methods:
- Collected 36 X-ray crystal structures of NcAA9D from a single crystal at cryogenic temperature.
- Analyzed structural changes and electron density variations with increasing X-ray dose.
- Investigated the photoreduction of copper(II) and displacement of water ligands.
Main Results:
- Characterized the dose-dependence of active-site geometry in NcAA9D.
- Observed X-ray dose impact on the electron density of pre-bound dioxygen species.
- Documented the displacement of water ligands from the copper active site due to photoreduction.
- Identified electron density smearing that can lead to misinterpretation of copper-bound dioxygen species.
Conclusions:
- Radiation-dose series from a single crystal are invaluable for studying radiation-sensitive enzymes like LPMOs.
- These data facilitate unambiguous assignment of radiation-sensitive intermediates at enzyme active sites.
- The findings improve the reliability of structural studies on LPMOs and other redox-active metalloenzymes.
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