Against the odds? De novo structure determination of a pilin with two cysteine residues by sulfur SAD

DOI: 10.1107/S1399004715003272
PMID: 25945575

Authors: Manuela Gorgel (Aarhus University) , Andreas Bøggild (Aarhus University) , Jakob Jensen Ulstrup (Aarhus University) , Manfred S. Weiss (Helmholtz Zentrum Berlin fur Materialien und Energie) , Uwe Müller (Helmholtz Zentrum Berlin fur Materialien und Energie) , Poul Nissen (Aarhus University) , Thomas Boesen (Aarhus University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section D Biological Crystallography , VOL 71 (5) , PAGES 1095 - 1101

State: Published (Approved)
Published: May 2015

Abstract: Exploiting the anomalous signal of the intrinsic S atoms to phase a proteinstructure is advantageous, as ideally only a single well diffracting native crystalis required. However, sulfur is a weak anomalous scatterer at the typicalwavelengths used for X-ray diffraction experiments, and therefore sulfur SADdata sets need to be recorded with a high multiplicity. In this study, the structureof a small pilin protein was determined by sulfur SAD despite several obstaclessuch as a low anomalous signal (a theoretical Bijvoet ratio of 0.9% at awavelength of 1.8 A˚), radiation damage-in duced reduction of the cysteines and amultiplic ity of only 5.5. The anomalous signal was improved by merging threedata sets from different volumes of a single crystal, yielding a multiplicity of 17.5,and a sodium ion was added to the substructure of anomalous scatterers. Ingeneral, all data sets were balanced around the threshold values for a successfulphasing strategy. In additi on, a collection of statistics on structures from thePDB that were solved by sulfur SAD are presented and compared with the data.Looking at the quality indicator Ranom/Rp.i.m., an inconsistency in thedocumentation of the anomalous R factor is noted and reported.

Journal Keywords: Pilin; S-SAD; de novo structure; determination

Subject Areas: Biology and Bio-materials


Instruments: I24-Microfocus Macromolecular Crystallography

Other Facilities: BESSY

Added On: 12/01/2016 13:40

Discipline Tags:

Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX) Single Wavelength Anomalous Diffraction (SAD)