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High-resolution Structure Determination (high-resolution + structure_determination)
Selected AbstractsHigh-resolution X-ray crystal structure of bovine H-protein at 0.88,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2010Akifumi Higashiura Recent technical improvements in macromolecular X-ray crystallography have significantly improved the resolution limit of protein structures. However, examples of high-resolution structure determination are still limited. In this study, the X-ray crystal structure of bovine H-protein, a component of the glycine cleavage system, was determined at 0.88,Å resolution. This is the first ultrahigh-resolution structure of an H-protein. The data were collected using synchrotron radiation. Because of limitations of the hardware, especially the dynamic range of the CCD detector, three data sets (high-, medium- and low-resolution data sets) were measured in order to obtain a complete set of data. To improve the quality of the merged data, the reference data set was optimized for merging and the merged data were assessed by comparing merging statistics and R factors against the final model and the number of visualized H atoms. In addition, the advantages of merging three data sets were evaluated. The omission of low-resolution reflections had an adverse effect on visualization of H atoms in hydrogen-omit maps. Visualization of hydrogen electron density is a good indicator for assessing the quality of high-resolution X-ray diffraction data. [source] A new crystal form of XT6 enables a significant improvement of its diffraction quality and resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004Maya Bar Xylanases (1,4-,- d -xylan xylanhydrolases; EC 3.2.1.8) hydrolyze the 1,4-,- d -xylopyranosyl linkage of xylans. The detailed structural characterization of these enzymes is of interest for the elucidation of their catalytic mechanism and for their rational modification toward improved stability and specificity. An extracellular xylanase from Geobacillus stearothermophilus T-6 (XT6) has recently been cloned, overexpressed, purified and biochemically characterized. Previous crystallographic efforts resulted in a hexagonal crystal form, which subsequently proved to be of limited use for structural analysis, mainly because of its relatively poor diffraction quality and resolution. A systematic search for more suitable crystals of XT6 recently resulted in a new crystal form of this enzyme with significantly improved diffraction characteristics. The new crystals belong to a C -centred monoclinic crystal system (space group C2), with unit-cell parameters a = 121.5, b = 61.7, c = 89.1,Å, , = 119.7°. These crystals diffract X-rays to better than 1.5,Å resolution, showing a very clear diffraction pattern of relatively high quality. The crystals are mechanically strong and exhibit excellent radiation-stability when frozen under cold nitrogen gas. A full diffraction data set to 1.45,Å resolution (94.1% completeness, Rmerge = 7.0%) has been collected from flash-frozen crystals of the native enzyme at 95,K using synchrotron radiation. Crystals of the E159A/E265A catalytic double mutant of XT6 were found to be isomorphous to those of native XT6. They were used for a full measurement of 1.8,Å resolution diffraction data at 100,K (90.9% completeness; Rmerge = 5.0%). These data are currently being used for the high-resolution structure determination of XT6 and its mutant for mechanistic interpretations and rational introduction of thermostability. [source] Crystallization and preliminary X-ray analysis of a thermoalkalophilic lipase from Bacillus stearothermophilus L1ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2001Seong-Tae Jeong A thermoalkalophilic lipase from Bacillus stearothermophilus L1 (L1 lipase) was crystallized in two different crystal forms using a low concentration of the enzyme and a calcium-exchange process. The first, needle-like, crystal form, which diffracts to about 3.5,Å, belongs to the orthorhombic space group P212121, with unit-cell parameters a = 67.84, b = 72.96, c = 104.41,Å. The second, monoclinic, crystal form, which behaves better than the first form for crystallographic analyses, belongs to the monoclinic space group C2 and has unit-cell parameters a = 119.62, b = 85.05, c = 98.36,Å, , = 99.73°. From the monoclinic crystals, a native data set and a samarium-derivative data set were collected to 2.0 and 2.3,Å resolution, respectively. The difference Patterson map between the two data sets shows strong heavy-atom peaks, indicating that the crystals are suitable for a high-resolution structure determination. [source] Preliminary X-ray data analysis of crystalline hibiscus chlorotic ringspot virusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Ao Cheng Hibiscus chlorotic ringspot virus (HCRSV) is a positive-sense monopartite single-stranded RNA virus that belongs to the Carmovirus genus of the Tombusviridae family, which includes carnation mottle virus (CarMV). The HCRSV virion has a 30,nm diameter icosahedral capsid with T = 3 quasi-symmetry containing 180 copies of a 38,kDa coat protein (CP) and encapsidates a full-length 3.9,kb genomic RNA. Authentic virus was harvested from infected host kenaf leaves and was purified by saturated ammonium sulfate precipitation, sucrose density-gradient centrifugation and anion-exchange chromatography. Virus crystals were grown in multiple conditions; one of the crystals diffracted to 3.2,Å resolution and allowed the collection of a partial data set. The crystal belonged to space group R32, with unit-cell parameters a = b = 336.4, c = 798.5,Å. Packing considerations and rotation-function analysis determined that there were three particles per unit cell, all of which have the same orientation and fixed positions, and resulted in tenfold noncrystallography symmetry for real-space averaging. The crystals used for the structure determination of southern bean mosaic virus (SBMV) have nearly identical characteristics. Together, these findings will greatly aid the high-resolution structure determination of HCRSV. [source] | ||||||||||