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Data collection with a tailored X‐ray beam size at 2.69 Å wavelength (4.6 keV): sulfur SAD phasing of Cdc23 Nterm
Author(s) -
Cianci Michele,
Groves Matthew R.,
Barford David,
Schneider Thomas R.
Publication year - 2016
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.374
H-Index - 138
ISSN - 2059-7983
DOI - 10.1107/s2059798315010268
Subject(s) - phaser , beamline , resolution (logic) , crystallography , synchrotron , crystal structure , crystal (programming language) , optics , x ray crystallography , wavelength , diffraction , materials science , chemistry , physics , beam (structure) , computer science , programming language , artificial intelligence
The capability to reach wavelengths of up to 3.1 Å at the newly established EMBL P13 beamline at PETRA III, the new third‐generation synchrotron at DESY in Hamburg, provides the opportunity to explore very long wavelengths to harness the sulfur anomalous signal for phase determination. Data collection at λ = 2.69 Å (4.6 keV) allowed the crystal structure determination by sulfur SAD phasing of Cdc23 Nterm , a subunit of the multimeric anaphase‐promoting complex (APC/C). At this energy, Cdc23 Nterm has an expected Bijvoet ratio ⟨| F anom |⟩/⟨ F ⟩ of 2.2%, with 282 residues, including six cysteines and five methionine residues, and two molecules in the asymmetric unit (65.4 kDa; 12 Cys and ten Met residues). Selectively illuminating two separate portions of the same crystal with an X‐ray beam of 50 µm in diameter allowed crystal twinning to be overcome. The crystals diffracted to 3.1 Å resolution, with unit‐cell parameters a = b = 61.2, c = 151.5 Å, and belonged to space group P 4 3 . The refined structure to 3.1 Å resolution has an R factor of 18.7% and an R free of 25.9%. This paper reports the structure solution, related methods and a discussion of the instrumentation.