Structure determination of VEGF-E by sulfur SAD

The crystal structure of VEGF-E was solved by the sulfur single-wavelength anomalous dispersion method (S-SAD) using highly redundant low-resolution data collected at a wavelength of lambda approximately 1.7 A with an estimated anomalous signal of 1.5%. 11 sulfur sites, nine out of 16 disulfide bonds and two out of 12 methionines could be located in the asymmetric unit using data truncated at a resolution of 4.1 A; however, none of the common diffraction data-quality indicators for SAD allowed clear discrimination between successful and unsuccessful resolution cutoffs. The high solvent content of 75% allowed efficient density modification to be performed and an unbiased electron-density map of good quality to be generated. This study demonstrates the strength of S-SAD for phasing using accurate highly redundant data at low resolution.