PDBsum entry 2oqu

Hydrolase

PDB id: 2oqu

Contents

Protein chain

240 a.a.

Ligands

SO4

Metals

_XE

_CA

Waters ×327

References listed in PDB file

Key reference

• Title: High-Pressure cryocooling for capillary sample cryoprotection and diffraction phasing at long wavelengths.
• Authors: C.U.Kim, Q.Hao, S.M.Gruner.
• Ref.: Acta Crystallogr D Biol Crystallogr, 2007, 63, 653-659. [DOI no: 10.1107/S0907444907011924]
• PubMed id: 17452791

Abstract

Crystal cryocooling is usually employed to reduce radiation damage during X-ray crystallography. Recently, a high-pressure cryocooling method has been developed which results in excellent diffraction-quality crystals without the use of penetrative cryoprotectants. Three new developments of the method are presented here: (i) Xe-He high-pressure cryocooling for Xe SAD phasing, (ii) native sulfur SAD phasing and (iii) successful cryopreservation of crystals in thick-walled capillaries without additional cryoprotectants other than the native mother liquor. These developments may be useful for structural solution of proteins without the need for selenomethionine incorporation and for high-throughput protein crystallography.

Figure 2.
Figure 2 He high-pressure cryocooling and S SAD phasing of thaumatin. (a) Thaumatin crystal in a polycarbonate capillary at 110 K. The entire sample, the crystal and mother liquor in the capillary, was He high-pressure cryocooled without adding penetrative cryoprotectants. This clear sample could not be obtained by conventional (room-pressure) flash-cryocooling when cryoprotectants were not added. (b) Diffraction image of the thaumatin crystal grown in a polycarbonate capillary that was He high-pressure cryocooled at 170 MPa. The diffuse background scatter from the capillary ranges from 4.5 to 5.5 Å. The lack of ice rings on the image confirms that water vitrification was successfully achieved under high pressure. The resolution limit [I/ (I) equal to] 5.0] is approximately 1.9 Å and the crystal mosaicity is 0.34°. The diffraction spots in the enlarged region look compact. (c) Anomalous difference map (5 level) generated with the refined phases. All 17 sulfurs that naturally present in thaumatin are clearly visible. The shape of the electron density at disulfide bonds is dumbbell-shaped, so two-sulfur positions could be easily distinguished. The peak height was over the 10 level (red) for most of the sulfur sites and the peak at Met112 was even visible at the 15 level. (d) F[o] electron-density map (1 level) after S SAD phasing and density modification at 1.9 Å resolution. The final refined model solved by molecular replacement was superimposed for visual map evaluation. The figure of merit is 0.824 and the map correlation coefficient calculated with the final refined 2F[o] - F[c] density map is 0.85 for the main chain and 0.76 for side chains.

The above figure is reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2007, 63, 653-659) copyright 2007.