Data Collection with a Tailored X-Ray Beam Size at 2.69 A Wavelength (4.6 Kev): Sulfur Sad Phasing of Cdc23Nterm
Cianci, M., Groves, M.R., Barford, D., Schneider, T.R.(2016) Acta Crystallogr D Biol Crystallogr 72: 403
- PubMed: 26960127 
- DOI: https://doi.org/10.1107/S2059798315010268
- Primary Citation of Related Structures:  
5FTP - PubMed Abstract: 
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〈|Fanom|〉/〈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 P43. The refined structure to 3.1 Å resolution has an R factor of 18.7% and an Rfree of 25.9%. This paper reports the structure solution, related methods and a discussion of the instrumentation.
Organizational Affiliation: 
EMBL, Notkestrasse 85, 22607 Hamburg, Germany.