W0290

32-kDa Protein Structure (One Se Site) Solved by using SAD Data Collected at the Structural Biology Center. R. Zhang, F.J. Rotella, R.W. Alkire, N.E.C. Duke, M. Zhou, G. Joachimiak and A. Joachimiak, Biosciences Div., Argonne National Laboratory, Argonne, IL 60439.

Insertion-device beamlines at third-generation synchrotron sources, such as Argonne’s Advanced Photon Source (APS), have expanded the capabilities of protein crystallography to include atomic- and near-atomic-resolution data collection, with the ability to collect complete data sets in a matter of minutes. Single-wavelength anomalous diffraction (SAD) experiments under these conditions can be completed in times ranging from minutes to an hour. Due to the properties of the anomalous signal, these experiments are capable of yielding unbiased phases and experimental electron density maps at atomic resolution. X-ray diffraction data from a crystalline hypothetical protein from Staphylococcus aureus were collected using the insertion-device beamline (19ID) and experiment facilities of the Structural Biology Center at the APS. SAD data were collected at the peak wavelength of the Se K-edge in 15 minutes employing inverse-beam geometry for the orthorhombic sample (P2₁2₁2₁, a = 40.50 Å, b = 73.88 Å, c = 92.25 Å, Z = 1, MW = 32 kDa). The data set covered a rotation range of 280° in 1° images with a 2-second exposure time per image. Diffraction from the sample was observed to a resolution of 1.7 Å. The images were processed using HKL2000.¹ The structure was phased from one Se site, and it was solved and refined using CNS.² Further details of data collection, structure solution and structure refinement will be presented.

¹Otwinowski, Z. and Minor, W. (1997). Methods Enzymol. 276, 307–326.

²Brünger, A. T., et al. (1998). Acta Crystallogr. D 54, 905–921.

This work was supported by the National Institutes of Health Grant GM62414-01 and the U. S. Department of Energy, Office of Biological and Environmental Research, under Contract W-31-109-ENG-38.