Determination of a Novel Structure by a Combination of Long-wavelength Sulfur Phasing and Radiation-damage-induced Phasing

The structure of the 115 amino-acid residue protein DsvC was determined based on the anomalous scattering provided by the five S atoms present in the structure. By collecting the diffraction data at a wavelength of 1.9 A, the anomalous signal provided by the S atoms was enhanced. However, significant radiation damage occurred during the course of the experiment, which led to differences between different parts of the data set. Only by dividing the total data set into five data sets was it possible to obtain phases; these could then be successfully extended to allow structure determination by the automated model-building program ARP/wARP. A computational correction for the radiation damage was found to significantly improve the success rate in determining the heavy-atom substructure and to improve phasing and refinement statistics.