Data collection and structure determination. The UCH37N crystals were suspended in
saha hdac rayon loop and flash cooled in liquid nitrogen. The native data sets were collected at 100 K. Multi-wavelength data were collected from a single SeUCH37N crystal. Both data sets were collected on a DIP6040 imaging plate detector at beamline BL44XU of SPring-8. All data sets were processed with the program HKL2000 [17]. The UCH37N crystal belongs to space group C2, with unit cell dimensions a = 67.58 ?, b = 57.06 ?, c = 48.74 ?, β = 100.91° with one UCH37N per asymmetric unit. The SeUCH37N crystal belongs to space group C2221, with unit cell dimensions a = 62.77 ?, b = 69.43 ?, c = 96.19 ? and with one SeUCH37N per asymmetric unit. The structure was determined by the multiwavelength anomalous dispersion (MAD) method with three different wavelengths to 3.15 ? resolution. The selenium sites determination, phase calculation, density-modification and partial model construction were executed by the program PHENIX [18]. The partially built model was improved manually using the graphical programs XtalView [19] and Coot [20]. The model constructed from MAD data was used for molecular replacement to determine the native structure, using the program MOLREP [21]. Refinement of the native structure was carried out using the programs CNS [22] and LAFIRE [23]. An Rfactor of 20.5% (Rfree = 25.5%) was achieved from the native data up to 2.2 ? resolution. The current refined model includes residues 7–145 and 162–226 of the 228 residues in the protein. Crystallographic data and refinement statistics are
plasmids listed in Table 1. Crystallographic coordinates and structure factors have been deposited at the Protein Data Bank with Accession codes 3A7S and RCSB028918, respectively.
