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Native Crystal (native + crystal)
Selected AbstractsThe purification, crystallization and preliminary structural characterization of FAD-dependent monooxygenase PhzS, a phenazine-modifying enzyme from Pseudomonas aeruginosaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2006Neelakshi Gohain The blue chloroform-soluble bacterial metabolite pyocyanin (1-hydroxy-5-methyl-phenazine) contributes to the survival and virulence of Pseudomonas aeruginosa, an important Gram-negative opportunistic pathogen of humans and animals. Little is known about the two enzymes, designated PhzM and PhzS, that function in the synthesis of pyocyanin from phenazine-1-carboxylic acid. In this study, the FAD-dependent monooxygenase PhzS was purified and crystallized from lithium sulfate/ammonium sulfate/sodium citrate pH 5.5. Native crystals belong to space group C2, with unit-cell parameters a = 144.2, b = 96.2, c = 71.7,Å, , = , = 90, , = 110.5°. They contain two monomers of PhzS in the asymmetric unit and diffract to a resolution of 2.4,Å. Seleno- l -methionine-labelled PhzS also crystallizes in space group C2, but the unit-cell parameters change to a = 70.6, b = 76.2, c = 80.2,Å, , = , = 90, , = 110.5° and the diffraction limit is 2.7,Å. [source] A description of the structural determination procedures of a gap junction channel at 3.5,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Michihiro Suga Intercellular signalling is an essential characteristic of multicellular organisms. Gap junctions, which consist of arrays of intercellular channels, permit the exchange of ions and small molecules between adjacent cells. Here, the structural determination of a gap junction channel composed of connexin 26 (Cx26) at 3.5,Å resolution is described. During each step of the purification process, the protein was examined using electron microscopy and/or dynamic light scattering. Dehydration of the crystals improved the resolution limits. Phase refinement using multi-crystal averaging in conjunction with noncrystallographic symmetry averaging based on strictly determined noncrystallographic symmetry operators resulted in an electron-density map for model building. The amino-acid sequence of a protomer structure consisting of the amino-terminal helix, four transmembrane helices and two extracellular loops was assigned to the electron-density map. The amino-acid assignment was confirmed using six selenomethionine (SeMet) sites in the difference Fourier map of the SeMet derivative and three intramolecular disulfide bonds in the anomalous difference Fourier map of the native crystal. [source] Crystallization of parasporin-2, a Bacillus thuringiensis crystal protein with selective cytocidal activity against human cellsACTA CRYSTALLOGRAPHICA SECTION D, Issue 12-2 2004Toshihiko Akiba Bacillus thuringiensis is a valuable source of protein toxins that are specifically effective against certain insects and worms but harmless to mammals. In contrast, a protein toxin obtained from B. thuringiensis strain A1547, designated parasporin-2, is not insecticidal but has a strong cytocidal activity against human cells with markedly divergent target specificity. The 37,kDa inactive protein is proteolytically activated to a 30,kDa active form. The active form of the recombinant protein toxin was crystallized in the presence of ethylene glycol and polyethylene glycol 8000 at neutral pH. The crystals belong to the hexagonal space group P61 or P65, with unit-cell parameters a = b = 134.37, c = 121.24,Å. Diffraction data from a native crystal were collected to 2.75,Å resolution using a synchrotron-radiation source. [source] Phase transition of triclinic hen egg-white lysozyme crystal associated with sodium bindingACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2004Kazuaki Harata A triclinic crystal of hen egg-white lysozyme obtained from a D2O solution at 313,K was transformed into a new triclinic crystal by slow release of solvent under a temperature-regulated nitrogen-gas stream. The progress of the transition was monitored by X-ray diffraction. The transition started with the appearance of strong diffuse streaks. The diffraction spots gradually fused and faded with the emergence of diffraction from the new lattice; the scattering power of the crystal fell to a resolution of 1.5,Å from the initial 0.9,Å resolution. At the end of the transition, the diffuse streaks disappeared and the scattering power recovered to 1.1,Å resolution. The transformed crystal contained two independent molecules and the solvent content had decreased to 18% from the 32% solvent content of the native crystal. The structure was determined at 1.1,Å resolution and compared with the native structure refined at the same resolution. The backbone structures of the two molecules in the transformed crystal were superimposed on the native structure with root-mean-square deviations of 0.71 and 0.96,Å. A prominent structural difference was observed in the loop region of residues Ser60,Leu75. In the native crystal, a water molecule located at the centre of this helical loop forms hydrogen bonds to main-chain peptide groups. In the transformed crystal, this water molecule is replaced by a sodium ion with octahedral coordination that involves water molecules and a nitrate ion. The peptide group connecting Arg73 and Asn74 is rotated by 180° so that the CO group of Arg73 can coordinate to the sodium ion. The change in the X-ray diffraction pattern during the phase transition suggests that the transition proceeds at the microcrystal level. A mechanism is proposed for the crystal transformation. [source] Structure of a conserved CoA-binding protein synthesized by a cell-free systemACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2003Takashi Wada TT1466 is a hypothetical protein from the extremely thermophilic bacterium Thermus thermophilus HB8 and is highly conserved in bacteria and archaea. The selenomethionyl protein was synthesized by a cell-free system and the crystal structure was determined at 2.0,Å by MAD phasing. A native crystal was used for structure refinement to 1.7,Å. The structure is highly homologous to that of the CoA-binding domain of the succinyl-CoA synthetase from Escherichia coli, despite the protein having only 14% sequence identity to this domain. An isothermal titration calorimetry experiment was performed to investigate whether TT1466 binds CoA and revealed high-affinity CoA binding of TT1466. [source] Purification, crystallization and preliminary X-ray analysis of the Enterococcus faecalis protein EF0377ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2003Alan Riboldi-Tunnicliffe The EF0377 gene of Enterococcus faecalis was cloned and overexpressed in Escherichia coli. The protein has been purified and crystallized in three forms. Type III crystals belong to space group P21, with unit-cell parameters a = 72.11, b = 94.97, c = 80.77,Å, , = 111.93°. There are four molecules per asymmetric unit and diffraction is observed to beyond 1.65,Å under cryoconditions (100,K) using synchrotron radiation. An almost complete set of X-ray diffraction data was collected to 1.9,Å from the native crystal. [source] Crystallization and preliminary crystallographic analysis of a partial extracellular fragment of a sperm membrane protein YWK-II/APPH related to the Alzheimer ,A4-amyloid precursor proteinACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2003Maojun Yang Crystals of a partial extracellular fragment of a human sperm membrane protein YWK-II/APPH have been grown at 291,K using PEG 4000 as precipitant. The diffraction pattern of the crystal extends to 2.8,Å resolution at 100,K using Cu,K, radiation. The crystals belong to space group P212121, with unit-cell parameters a = 46.009, b = 67.387, c = 149.241,Å, , = , = , = 90°. The presence of two molecules per asymmetric unit gives a crystal volume per protein mass (VM) of 3.51,Å3,Da,1 and a solvent content of 64.6% by volume. A full set of X-ray diffraction data were collected to 2.8,Å resolution from the native crystal. [source] Generating isomorphous heavy-atom derivatives by a quick-soak method.ACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2002Part II: phasing of new structures A quick-soak method has been applied to generate de novo heavy-atom phasing to solve two new protein structures, a type II transforming growth factor , receptor (TBRII) and a natural killer cell receptor,ligand complex, NKG2D,ULBP3. In the case of TBRII, a crystal derivatized for only 10,min in saturated HgCl2 provided adequate phasing for structure determination. Comparison between HgCl2 derivatives generated by 10,min soaking and by 12,h soaking revealed similar phasing statistics. The shorter soak, however, resulted in a derivative more isomorphous to the native than the longer soak as judged by changes in the unit-cell parameter a upon derivatization as well as by the quality of a combined SIRAS electron-density map. In the case of the NKG2D,ULBP3 structure, all overnight soaks in heavy-atom solutions resulted in crystal lattice disorder and only the quick soaks preserved diffraction. Despite fragile lattice packing, the quick-soaked K2PtCl4 derivative was isomorphous with the native crystal and the electron-density map calculated from combined SIR and MAD phases is better than that calculated from MAD phases alone. Combined with mass-spectrometry-assisted solution heavy-atom derivative screening and the use of synchrotron radiation, the quick-soak derivatization has the potential to transform the time-consuming conventional heavy-atom search into a real-time `on-the-fly' derivatization process that will benefit high-throughput structural genomics. [source] Crystals of ternary protein,DNA complexes composed of DNA-binding domains of c-Myb or v-Myb, C/EBP, or C/EBP, and tom-1A promoter fragmentACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2001Tahir H. Tahirov c-Myb and the C/EBP family are transcriptional regulatory factors that act in concert to regulate the expression of myeloid-specific genes. v-Myb encoded by avian myeloblastosis virus (AMV) is a mutated form of c-Myb that contains point mutations which disrupt the cooperation with C/EBPs. To understand the mechanism of the transcriptional synergy between c-Myb and C/EBPs and the effect of the v-Myb mutations on that synergy, knowledge based on their three-dimensional structures is essential. Crystals of ternary complexes, in which various combinations of the DNA-binding domains of c-Myb or v-Myb and C/EBP, or C/EBP, are bound to a DNA fragment from tom-1A promoter, were obtained by the vapour-diffusion method. Complete diffraction data sets were obtained from each native crystal and two types of iodine-derivative crystals. A three-wavelength MAD data set was also obtained from a bromine-derivative crystal. [source] Atomic resolution structure of Escherichia coli dUTPase determined ab initioACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2001A. González Cryocooled crystals of a mercury complex of Escherichia coli dUTPase diffract to atomic resolution. Data to 1.05,Å resolution were collected from a derivative crystal and the structure model was derived from a Fourier map with phases calculated from the coordinates of the Hg atom (one site per subunit of the trimeric enzyme) using the program ARP/wARP. After refinement with anisotropic temperature factors a highly accurate model of the bacterial dUTPase was obtained. Data to 1.45,Å from a native crystal were also collected and the 100,K structures were compared. Inspection of the refined models reveals that a large part of the dUTPase remains rather mobile upon freezing, with 14% of the main chain being totally disordered and with numerous side chains containing disordered atoms in multiple discrete conformations. A large number of those residues surround the active-site cavity. Two glycerol molecules (the cryosolvent) occupy the deoxyribose-binding site. Comparison between the native enzyme and the mercury complex shows that the active site is not adversely affected by the binding of mercury. An unexpected effect seems to be a stabilization of the crystal lattice by means of long-range interactions, making derivatization a potentially useful tool for further studies of inhibitor,substrate-analogue complexes of this protein at very high resolution. [source] Crystallization and preliminary X-ray crystallographic analysis of MinE, the cell-division topological specificity factor from Helicobacter pyloriACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2010Gil Bu Kang Cell division in Gram-negative bacteria is driven by the formation of an FtsZ ring at the division site. MinE regulates the proper placement of the FtsZ ring at mid-cell by blocking the inhibitory action of the MinCD complex. Diffraction data were collected at 2.8,Å resolution from a native crystal of full-length Helicobacter pylori MinE. The crystal belonged to space group P64. Assuming the presence of two molecules in the asymmetric unit, the calculated Matthews coefficient was 2.58,Å3,Da,1, which corresponds to a solvent content of 52.3%. For MAD phasing, a four-wavelength data set was collected at 3.0,Å resolution. [source] Crystallization and preliminary X-ray crystallographic analysis of free methionine-(R)-sulfoxide reductase from Staphylococcus aureusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009Seoung Min Bong Free methionine-(R)-sulfoxide reductase (fRMsr) catalyzes the reduction of the free form of methionine-(R)-sulfoxide back to free methionine. The fRMsr protein from Staphylococcus aureus was overexpressed in Escherichia coli, purified and crystallized at 295,K using ammonium sulfate as a precipitant. Diffraction data were collected to 1.7,Å resolution from a native crystal using synchrotron radiation. The crystal belonged to the hexagonal space group P6122, with unit-cell parameters a = b = 89.84, c = 88.75,Å, , = , = 90, , = 120°. Assuming the presence of one molecule in the asymmetric unit, the calculated Matthews coefficient value was 2.21,Å3,Da,1, with a solvent content of 57.1%. [source] Proteins can convert to ,-sheet in single crystalsPROTEIN SCIENCE, Issue 5 2004Run Zheng TC: transcarboxylase; 5S: a subunit of TC that carboxylates pyruvate; 12S: a subunit of TC that transfers carboxylate from methylmalonyl-CoA to biotin; Ni-NTA: a nickel-charged agarose resin Abstract Raman microscopy was used to follow conformational changes in single protein crystals. Crystals of native insulin and of the 5S and 12S subunits of the enzyme transcarboxylase showed a mixture of Raman marker bands signifying ,-helix, ,-sheet and nonordered secondary structure. However, by reducing the S,S bonds in the insulin crystal, or by lowering the pH for the 5S crystal, or by soaking substrates into the 12S crystal, the secondary structure in each crystal became predominantly ,-sheet. The ,-form crystals could be dissolved only with difficulty and yielded high,molecular weight protein aggregates, indicating that the ,-sheet formation involves intermolecular contacts. Although their morphology appeared unchanged, the crystals no longer diffracted X-rays. Using crystals that had not been exposed to laser light, the dye thioflavin T formed highly fluorescent complexes with the ",-transformed" crystals but not with the native crystals. [source] Structure of d -tyrosyl-tRNATyr deacylase using home-source Cu,K, and moderate-quality iodide-SAD data: structural polymorphism and HEPES-bound enzyme statesACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2010Manickam Yogavel d -Tyrosyl-tRNATyr deacylase (DTD) is an editing enzyme that removes d -amino acids from mischarged tRNAs. The crystal structure of Plasmodium falciparum DTD (PfDTD) was determined using the iodide-SAD phasing method. Iodide-derivatized PfDTD crystals were obtained using the quick cryo-soaking procedure in which native crystals were soaked for a short period of 10,30,s in cryoprotectant solution containing 0.2,1,M NaI. Iodide-SAD data sets were collected to 3.3 and 2.74,Å resolution from PfDTD crystals that belonged to two different space groups, P43 and P1, using an in-house X-ray copper-anode source. This is the first report to detail structure solution using low iodide anomalous signal, modest resolution and redundancy and average solvent content for SAD phasing of 984 and 1312 amino acids in the triclinic P1 and tetragonal P43 space groups, respectively. A total of 85% and 56% of the residues were automatically built into the iodide-phased electron-density maps using PHENIX AutoBuild. The structure of HEPES-bound PfDTD was subsequently determined by molecular replacement and refined to 2.83,Å resolution. The crystals obtained from various batches of crystallization trials of PfDTD exhibited polymorphism in terms of belonging to different crystal forms and space groups. Even within a given crystal system the unit-cell parameters showed high non-isomorphism. These packing variations were exploited in order to conduct a systematic study of conformational changes in PfDTD. It is shown that the disposition of a ten-residue insertion loop affects packing within the PfDTD crystals and seems to determine the non-isomorphism in unit-cell parameters. By tracking the changes in PfDTD unit cells, it was possible to map conformational differences within PfDTD that may be of significance for enzyme activity. [source] To scavenge or not to scavenge: that is the questionACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009Elzbieta Nowak Analysis of a series of diffraction data sets measured from four native as well as four nicotinic acid-soaked crystals of trypsin at 100,K shows a high variability in radiation-sensitivity among individual crystals for both nicotinic acid-soaked and native crystals. The level of radiation-sensitivity and the extent of its variability is statistically indistinguishable between the two conditions. This suggests that this potential scavenger does not have any statistically significant effect on the amount of radiation damage incurred in the crystals on X-ray irradiation. This is in contrast to previous results [Kauffmann et al. (2006), Structure, 14, 1099,1105] where only one crystal specimen was used for each condition (native and nicotinic acid-soaked). [source] Iodide-SAD, SIR and SIRAS phasing for structure solution of a nucleosome assembly proteinACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009Manickam Yogavel The crystal structure of Plasmodium falciparum nucleosome assembly protein (PfNapL) was determined by iodide-SAD/SIRAS phasing methods using iodide-SAD data to 3.0,Å resolution and native data to 2.4,Å resolution. Halide-derivatized PfNapL crystals were obtained using the quick cryo-soaking method in which the native crystals were soaked in a cryosolution consisting of 500,mM NaI for a short period of 30,60,s and data were collected at an in-house X-ray source using Cu,K, radiation. Despite a low anomalous signal-to-noise ratio of <1.2 in the >3.5,Å resolution bin, the data were sufficient to determine the structure by SAD/SIR/SIRAS methods using the soaked iodides. Previously, structure solution had failed with both molecular-replacement and selenomethionine-derivatization techniques owing to reasons that are detailed in this work. The phasing at low resolution with three iodides per monomer with high temperature factors was successful using any of the SAD, SIR or SIRAS methods. [source] Crystallization and preliminary X-ray crystallographic analysis of the [NiFe]-hydrogenase maturation factor HypF1 from Ralstonia eutropha H16ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Gordon Winter The hydrogenase maturation factor HypF1 is a truncated but functional version of the HypF protein. HypF is known to be involved in the supply of the CN, ligands of the active site of [NiFe]-hydrogenases, utilizing carbamoyl phosphate as a substrate. The first crystallization and preliminary X-ray studies of HypF1 from Ralstonia eutropha H16 are reported here. Crystals of HypF1 (394 amino acids, 40.7,kDa) were obtained by the sitting-drop vapour-diffusion technique using sodium formate as a precipitant. The crystals belonged to space group I222, with unit-cell parameters a = 79.7, b = 91.6, c = 107.2,Å. Complete X-ray diffraction data sets were collected at 100,K from native crystals and from a platinum derivative to a maximum resolution of 1.65,Å. [source] Crystallization and heavy-atom derivatization of StHsp14.0, a small heat-shock protein from Sulfolobus tokodaiiACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2009Takuro Hayashi Small heat-shock proteins (sHsps) bind and stabilize proteins denatured by heat or other stresses in order to prevent unfavourable protein aggregation. StHsp14.0 is an sHsp found in the acidothermophilic archaeon Sulfolobus tokodaii. A variant of StHsp14.0 was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted X-rays to 1.85,Å resolution and belonged to space group P21212, with unit-cell parameters a = 40.4, b = 61.1, c = 96.1,Å. The VM value was estimated to be 2.1,Å3,Da,1, assuming the presence of two molecules in the asymmetric unit. Heavy-atom derivative crystals were prepared successfully by the cocrystallization method and are isomorphic to native crystals. [source] Purification, crystallization and preliminary X-ray crystallographic studies of the complex between Smc5 and the SUMO E3 ligase Mms21ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2009Xinyuan Duan Smc5/6, a protein complex that belongs to the structural maintenance of chromosome (SMC) family, plays a key role in DNA replication, sister chromatid recombination and DNA damage repair. The complex contains eight subunits, including a SUMO E3 ligase Mms21 (Nse2). The activity of Mms21 is important for regulation of Smc5/6 in the response to DNA damage. Mms21 and the Mms21-binding region of Smc5 were overexpressed and purified individually in Escherichia coli with a C-terminal LEHHHHHH tag. The Mms21,Smc5 protein complex was crystallized. The diffraction of the crystals was improved greatly by glutaraldehyde treatment. X-ray diffraction data sets were collected to resolutions of 2.3 and 3.9,Å from native and selenomethionine-derivative protein crystals, respectively. The crystals belonged to space group C2221, with unit-cell parameters a = 47.465, b = 97.574, c = 249.215,Å for the native crystals. [source] Crystallization and preliminary crystallographic analysis of thermophilic cellulase from Fervidobacterium nodosum Rt17-B1ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009Baisong Zheng FnCel5A, a thermostable endoglucanase, is a member of glycohydrolase family 5 which catalyzes the hydrolysis of cellulose to glucose in the thermophilic bacterium Fervidobacterium nodosum Rt17-B1. FnCel5A is particularly interesting because of its high thermostability (Topt = 353,K, half-life 48,h) and its high specific activity towards carboxymethylcellulose. These properties make FnCel5A an attractive target for protein engineering to improve cellulase activity. In order to resolve the crystal structure of FnCel5A and to gain a better understanding of its biological function, recombinant FnCel5A was expressed, purified and crystallized at 291,K using NaH2PO4/KH2PO4 as a precipitant. A 2.4,Å resolution native data set was collected from a single flash-cooled crystal (100,K) using 20%(v/v) glycerol as a cryoprotectant. These crystals belonged to space group P21212, with unit-cell parameters a = 53.5, b = 81.7, c = 85.2,Å, , = , = , = 90°. One molecule is assumed to be present per asymmetric unit, which gives a Matthews coefficient of 2.5,Å3,Da,1. A data set was also collected to 1.7,Å resolution from a selenomethionyl derivative; it belonged to space group P212121 with the same unit-cell parameters as the native crystals. [source] Crystallization and preliminary X-ray analysis of FliJ, a cytoplasmic component of the flagellar type III protein-export apparatus from Salmonella sp.ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2009Tatsuya Ibuki The axial component proteins of the bacterial flagellum are synthesized in the cytoplasm and then translocated into the central channel of the flagellum by the flagellar type III protein-export apparatus for self-assembly at the distal growing end of the flagellum. FliJ is an essential cytoplasmic component of the export apparatus. In this study, Salmonella FliJ with an extra three residues (glycine, serine and histidine) attached to the N-terminus as the remainder of a His tag (GSH-FliJ) was purified and crystallized. Crystals were obtained by the sitting-drop vapour-diffusion technique using PEG 300 as a precipitant. GSH-FliJ crystals grew in the hexagonal space group P6122 or P6522. While the native crystals diffracted to 3.3,Å resolution, the diffraction resolution limit of mercury derivatives was extended to 2.1,Å. Anomalous and isomorphous difference Patterson maps of the mercury-derivative crystal showed significant peaks in their Harker sections, indicating the usefulness of the derivative data for structure determination. [source] Purification, crystallization and preliminary X-ray diffraction analysis of human Gadd45,ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2008Wenzheng Zhang Gadd45, MyD118 and CR6 (also termed Gadd45,, Gadd45, and Gadd45,, respectively) comprise a family of proteins that play important roles in negative growth control, maintenance of genomic stability, DNA repair, cell-cycle control and apoptosis. Recombinant human Gadd45, and its selenomethionine derivative were expressed in an Escherichia coli expression system and purified; they were then crystallized using the hanging-drop vapour-diffusion method. Diffraction-quality crystals were grown at 291,K using PEG 3350 as precipitant. Using synchrotron radiation, the best diffraction data were collected to 2.3,Å resolution for native crystals at 100,K; selenomethionyl derivative data were collected to 3.3,Å resolution. All the crystals belonged to space group I213, with approximate unit-cell parameters a = b = c = 126,Å. [source] Crystallization and preliminary X-ray analysis of a novel Kunitz-type kallikrein inhibitor from Bauhinia bauhinioidesACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2005Marcos Vicente de A. S. Navarro A Kunitz-type protease inhibitor (BbKI) found in Bauhinia bauhinioides seeds has been overexpressed in Escherichia coli and crystallized at 293,K using PEG 4000 as the precipitant. X-ray diffraction data have been collected to 1.87,Å resolution using an in-house X-ray generator. The crystals of the recombinant protein (rBbKI) belong to the orthorhombic space group P212121, with unit-cell parameters a = 46.70, b = 64.14, c = 59.24,Å. Calculation of the Matthews coefficient suggests the presence of one monomer of rBbKI in the asymmetric unit, with a corresponding solvent content of 51% (VM = 2.5,Å3,Da,1). Iodinated crystals were prepared and a derivative data set was also collected at 2.1,Å resolution. Crystals soaked for a few seconds in a cryogenic solution containing 0.5,M NaI were found to be reasonably isomorphous to the native crystals. Furthermore, the presence of iodide anions could be confirmed in the NaI-derivatized crystal. Data sets from native and derivative crystals are being evaluated for use in crystal structure determination by means of the SIRAS (single isomorphous replacement with anomalous scattering) method. [source] |