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Merohedrally Twinned (merohedrally + twinned)
Selected AbstractsMultiple isomorphous replacement on merohedral twins: structure determination of deacetoxycephalosporin C synthaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2001Anke C. Terwisscha van Scheltinga Merohedral twinning is a packing anomaly that seriously impairs the determination of macromolecular crystal structures. Crystals of deacetoxycephalosporin C synthase (DAOCS), an enzyme involved in the expansion of the penicillin nucleus to form the core structure of the cephalosporin antibiotics, were found to be merohedrally twinned by many diagnostic criteria. Here, the structure determination of DAOCS from twinned crystals based on a combination of isomorphous replacement and the use of a multiple-wavelength diffraction data set is described. [source] X-ray analysis of bilirubin oxidase from Myrothecium verrucaria at 2.3,Å resolution using a twinned crystalACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2010Kimihiko Mizutani Bilirubin oxidase (BOD), a multicopper oxidase found in Myrothecium verrucaria, catalyzes the oxidation of bilirubin to biliverdin. Oxygen is the electron acceptor and is reduced to water. BOD is used for diagnostic analysis of bilirubin in serum and has attracted considerable attention as an enzymatic catalyst for the cathode of biofuel cells that work under neutral conditions. Here, the crystal structure of BOD is reported for the first time. Blue bipyramid-shaped crystals of BOD obtained in 2-methyl-2,4-pentanediol (MPD) and ammonium sulfate solution were merohedrally twinned in space group P63. Structure determination was achieved by the single anomalous diffraction (SAD) method using the anomalous diffraction of Cu atoms and synchrotron radiation and twin refinement was performed in the resolution range 33,2.3,Å. The overall organization of BOD is almost the same as that of other multicopper oxidases: the protein is folded into three domains and a total of four copper-binding sites are found in domains 1 and 3. Although the four copper-binding sites were almost identical to those of other multicopper oxidases, the hydrophilic Asn residue (at the same position as a hydrophobic residue such as Leu in other multicopper oxidases) very close to the type I copper might contribute to the characteristically high redox potential of BOD. [source] Purification and crystallization of Phd, the antitoxin of the phd/doc operonACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Abel Garcia-Pino The antitoxin Phd from the phd/doc module of bacteriophage P1 was crystallized in two distinct crystal forms. Crystals of His-tagged Phd contain a C-terminally truncated version of the protein and diffract to 2.20,Å resolution. Crystals of untagged Phd purified from the Phd,Doc complex diffract to 2.25,Å resolution. These crystals are partially merohedrally twinned and contain the full-length version of the protein. [source] Purification, crystallization and preliminary X-ray diffraction analysis of disease-related mutants of p97ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009Wai-Kwan Tang The human type II AAA+ protein p97 participates in various cellular activities, presumably through its involvement in the ubiquitin,proteasome degradation pathway. Mutations in p97 have been implicated in patients with inclusion-body myopathy associated with Paget's disease of the bone and frontotemporal dementia (IBMPFD). In this work, three mutant p97 N-D1 fragments, R86A, R95G and R155H, were crystallized in the presence of ATP,S with PEG 3350 as a main precipitant, yielding two different crystal forms. The R155H mutant crystal belonged to space group R3, with unit-cell parameters in the hexagonal setting of a = b = 134.2, c = 182.9,Å, and was merohedrally twinned, with an estimated twin fraction of 0.34. The crystals of the R86A and R95G mutants belonged to space group P1, with similar unit-cell parameters of a = 90.89, b = 102.6, c = 107.2,Å, , = 97.5, , = 90.6, , = 91.5° and a = 92.76, b = 103.7, c = 107.7,Å, , = 97.7, , = 91.9, , = 89.7°, respectively. [source] Expression, purification and crystallization of the ecto-enzymatic domain of rat E-NTPDase1 CD39ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2008Xiaotian Zhong CD39 is a prototype member of the ecto-nucleoside triphosphate diphosphohydrolase family that hydrolyzes extracellular nucleoside diphosphates and triphosphates in the presence of divalent cations. Here, the expression, purification and crystallization of the ecto-enzymatic domain of rat CD39, sCD39, are described. The 67,kDa secreted soluble glycoprotein was recombinantly overexpressed in a glycosylation mutant CHO line, Lec.3.2.8.1, and purified from conditioned media. Diffraction-quality crystals of sCD39 were produced by the vapor-diffusion method using PEG 3350 and ammonium dihydrogen phosphate as precipitants. The enzyme crystallized in a primitive trigonal form in space group P32, with unit-cell parameters a = b = 118.1, c = 81.6,Å and with two sCD39 copies in the asymmetric unit. Several low- to medium-resolution diffraction data sets were collected using an in-house X-ray source. Analysis of the intensity statistics showed that the crystals were invariably merohedrally twinned with a high twin fraction. For initial phasing, a molecular-replacement search was performed against the complete 3.2,Å data set using a maximum-likelihood molecular-replacement method as implemented in Phaser. The initial model of the two sCD39 monomers was placed into the P32 lattice and rigid-body refined and position-minimized with PHENIX. [source] | ||||||||||