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Crystal structure of gluconate 5-dehydrogenase from Lentibacter algarum

Gluconate 5-dehydrogenase (Ga5DH; EC 1.1.1.69) from Lentibacter algarum (LaGa5DH) was recombinantly expressed in Escherichia coli and purified to homogeneity. The protein was crystallized and the crystal structure was solved at 2.1 Å resolution. The crystal belonged to the monoclinic system, with space group P1 and unit-cell parameters a = 55.42, b = 55.48, c = 79.16 Å, α = 100.51, β = 105.66, γ = 97.99°. The structure revealed LaGaDH to be a tetramer, with each subunit consisting of six α-helices and three antiparallel β-hairpins. LaGa5DH has high structural similarity to other Ga5DH proteins, demonstrating that this enzyme is highly conserved.




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Crystallographic snapshots of the EF-hand protein MCFD2 complexed with the intracellular lectin ERGIC-53 involved in glycoprotein transport

The transmembrane intracellular lectin ER–Golgi intermediate compartment protein 53 (ERGIC-53) and the soluble EF-hand multiple coagulation factor deficiency protein 2 (MCFD2) form a complex that functions as a cargo receptor, trafficking various glycoproteins between the endoplasmic reticulum (ER) and the Golgi apparatus. It has been demonstrated that the carbohydrate-recognition domain (CRD) of ERGIC-53 (ERGIC-53CRD) interacts with N-linked glycans on cargo glycoproteins, whereas MCFD2 recognizes polypeptide segments of cargo glycoproteins. Crystal structures of ERGIC-53CRD complexed with MCFD2 and mannosyl oligosaccharides have revealed protein–protein and protein–sugar binding modes. In contrast, the polypeptide-recognition mechanism of MCFD2 remains largely unknown. Here, a 1.60 Å resolution crystal structure of the ERGIC-53CRD–MCFD2 complex is reported, along with three other crystal forms. Comparison of these structures with those previously reported reveal that MCFD2, but not ERGIC-53–CRD, exhibits significant conformational plasticity that may be relevant to its accommodation of various polypeptide ligands.




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Crystal structure of the nucleoid-associated protein Fis (PA4853) from Pseudomonas aeruginosa

Factor for inversion stimulation (Fis) is a versatile bacterial nucleoid-associated protein that can directly bind and bend DNA to influence DNA topology. It also plays crucial roles in regulating bacterial virulence factors and in optimizing bacterial adaptation to various environments. Fis from Pseudomonas aeruginosa (PA4853, referred to as PaFis) has recently been found to be required for virulence by regulating the expression of type III secretion system (T3SS) genes. PaFis can specifically bind to the promoter region of exsA, which functions as a T3SS master regulator, to regulate its expression and plays an essential role in transcription elongation from exsB to exsA. Here, the crystal structure of PaFis, which is composed of a four-helix bundle and forms a homodimer, is reported. PaFis shows remarkable structural similarities to the well studied Escherichia coli Fis (EcFis), including an N-terminal flexible loop and a C-terminal helix–turn–helix (HTH) motif. However, the critical residues for Hin-catalyzed DNA inversion in the N-terminal loop of EcFis are not conserved in PaFis and further studies are required to investigate its exact role. A gel-electrophoresis mobility-shift assay showed that PaFis can efficiently bind to the promoter region of exsA. Structure-based mutagenesis revealed that several conserved basic residues in the HTH motif play essential roles in DNA binding. These structural and biochemical studies may help in understanding the role of PaFis in the regulation of T3SS expression and in virulence.





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Structure-based screening of binding affinities via small-angle X-ray scattering

Protein–protein and protein–ligand interactions often involve conformational changes or structural rearrangements that can be quantified by solution small-angle X-ray scattering (SAXS). These scattering intensity measurements reveal structural details of the bound complex, the number of species involved and, additionally, the strength of interactions if carried out as a titration. Although a core part of structural biology workflows, SAXS-based titrations are not commonly used in drug discovery contexts. This is because prior knowledge of expected sample requirements, throughput and prediction accuracy is needed to develop reliable ligand screens. This study presents the use of the histidine-binding protein (26 kDa) and other periplasmic binding proteins to benchmark ligand screen performance. Sample concentrations and exposure times were varied across multiple screening trials at four beamlines to investigate the accuracy and precision of affinity prediction. The volatility ratio between titrated scattering curves and a common apo reference is found to most reliably capture the extent of structural and population changes. This obviates the need to explicitly model scattering intensities of bound complexes, which can be strongly ligand-dependent. Where the dissociation constant is within 102 of the protein concentration and the total exposure times exceed 20 s, the titration protocol presented at 0.5 mg ml−1 yields affinities comparable to isothermal titration calorimetry measurements. Estimated throughput ranges between 20 and 100 ligand titrations per day at current synchrotron beamlines, with the limiting step imposed by sample handling and cleaning procedures.




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Chirality in Biological Nanospaces: Reactions in Active Sites. By Nilashis Nandi. Pp. 209. CRC Press, 2011. Price £79.99. ISBN 9781439840023.




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Visualization Bench for the screening of crystallization assays and the automation of in situ experiments




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Solution structure and assembly of β-amylase 2 from Arabidopsis thaliana

Solution structure of β-amylase 2 from Arabidopsis thaliana shows the role of the conserved N-terminus in enzyme tetramer formation.




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Industrial cryo-EM facility setup and management

The setup and operation of an industrial cryo-EM laboratory is described.




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Exploring the complex map of insulin polymorphism: a novel crystalline form in the presence of m-cresol

A novel monoclinic phase of human insulin co-crystallized with m-cresol was structurally characterized by means of powder and single-crystal X-ray diffraction.




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Confidence maps: statistical inference of cryo-EM maps

The concept of statistical signal detection by controlling the false-discovery rate (FDR) to aid the atomic model interpretation of cryo-EM density maps is reviewed. The recommended usage of the FDR software tool is presented together with its successful integration into the CCP-EM suite.




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The crystal structure of the heme d1 biosynthesis-associated small c-type cytochrome NirC reveals mixed oligomeric states in crystallo

The crystal structure of the c-type cytochrome NirC from Pseudomonas aeruginosa has been determined and reveals the simultaneous presence of monomers and 3D domain-swapped dimers in the same asymmetric unit.




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Scaling diffraction data in the DIALS software package: algorithms and new approaches for multi-crystal scaling

A new scaling program is presented with new features to support multi-sweep workflows and analysis within the DIALS software package.




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Crystal and solution structures of fragments of the human leucocyte common antigen-related protein

The crystal and solution SAXS structures of a fragment of human leucocyte common antigen-related protein show that it is less flexible than the homologous proteins tyrosine phosphatase receptors δ and σ.




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Structure of P46, an immunodominant surface protein from Mycoplasma hyopneumoniae: interaction with a monoclonal antibody

Structures of the immunodominant protein P46 from M. hyopneumoniae has been determined by X-ray crystallography and it is shown that P46 can bind a diversity of oligosaccharides, particularly xylose, which exhibits a very high affinity for this protein. Structures of a monoclonal antibody, both alone and in complex with P46, that was raised against M. hyopnemoniae cells and specifically recognizes P46 are also reported.




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Structural and thermodynamic analysis of interactions between death-associated protein kinase 1 and anthraquinones

Death-associated protein kinase 1 (DAPK1) was found to form a complex with purpurin and the crystal structure of the complex was determined. Purpurin may be a good lead compound for for the discovery of inhibitors of DAPK1.




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Bond-valence analyses of the crystal structures of FeMo/V cofactors in FeMo/V proteins

The bond-valence method was performed on 51 crystal data sets from nitrogenase proteins, indicating the presence of molybdenum(III) in FeMo cofactors and vanadium(III) with more reduced iron complements in FeV cofactors.




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Structure of ClpC1-NTD in complex with the anti-TB natural product ecumicin reveals unique binding interactions

Comparison of the structures of ClpC1-Ecumicin and ClpC1-Rufomycin reveals unique interaction relevant to the mode of action.




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Structural basis of carbohydrate binding in domain C of a type I pullulanase from Paenibacillus barengoltzii




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Structure–function study of AKR4C14, an aldo-keto reductase from Thai Jasmine rice (Oryza sativa L. ssp. Indica cv. KDML105)

Rice AKR in the apo structure reveals the ordered open conformation and its key residues which form the substrate channel wall and determine its substrate preference for straight-chain aldehydes.




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Macromolecular X-ray crystallography: soon to be a road less travelled?

From the perspective of a young(ish) structural biologist who currently specialises in macromolecular X-ray crystallography, are the best years of crystallography over? Some evidence and hopefully thought-provoking analysis is presented here on the subject.




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Structure of Thermococcus litoralis Δ1-pyrroline-2-carboxylate reductase in complex with NADH and L-proline

The paper reports the structure of a Δ1-pyrroline-2-carboxylate reductase from the archaeon Thermococcus litoralis, a key enzyme involved in the second step of trans-4-Hydroxy-L-proline metabolism, conserved in archaea, bacteria and humans.




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Crystal structure of bis­(1-ethyl-1H-imidazole-κN3)(meso-tetra­mesitylporphyrinato-κ4N,N',N'',N''')iron(III) perchlorate chloro­benzene sesquisolvate

In the complex cation of title compound, [Fe(C56H52N4)(C5H8N2)2]ClO4·1.5C6H5Cl, the ironIII atom is coordinated in a distorted octa­hedral manner by four pyrrole N atoms of the porphyrin ring system in the equatorial plane, and by two N atoms of the 1-ethyl­imidazole ligands in the axial sites. A disordered perchlorate anion and one and a half chloro­benzene solvent mol­ecules are also present. The cationic complex exhibits a highly ruffled porphyrin core. The average Fe—Np (Np is a porphyrin N atom) bond length is 1.988 (5), and the axial Fe—NIm (NIm is an imidazole N atom) bond lengths are 1.962 (3) and 1.976 (3) Å. The two 1-ethyl­imidazole ligands are inclined to each other by a dihedral angle of 68.62 (16)°. The dihedral angles between the 1-ethyl­imidazole planes and the planes of the closest Fe—Np vector are 28.52 (18) and 43.57 (13)°. Inter­molecular C—H⋯Cl inter­actions are observed.




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Redetermination of the crystal structure of BaTeO3(H2O), including the localization of the hydrogen atoms

The redetermination of the crystal structure of barium oxidotellurate(IV) monohydrate allowed the localization of the hydrogen atoms that were not determined in the previous study [Nielsen, Hazell & Rasmussen (1971). Acta Chem. Scand. 25, 3037–3042], thus making an unambiguous assignment of the hydrogen-bonding scheme possible. The crystal structure shows a layered arrangement parallel to (001), consisting of edge-sharing [BaO6(H2O)] polyhedra and flanked by isolated [TeO3] trigonal pyramids on the top and bottom. O—H⋯O hydrogen bonds of medium strength link adjacent layers along [001].




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Crystal structure of bis­(benzoato-κO)[5,15-diphenyl-10,20-bis­(pyridin-4-yl)porphyrinato-κ4N,N',N'',N''']tin(IV)

In the crystal structure of the title compound, [Sn(C42H26N6)(C7H5O2)2], the SnIV ion is located on a crystallographic inversion centre and is octa­hedrally coordinated with an N4O2 set. Four N atoms of the porphyrin ring form the equatorial plane while the axial positions are occupied by two O atoms from benzoate anions. The molecular packing of the title complex involves non-classical hydrogen bonds of the types C—H⋯O and C—H⋯N, leading to a three-dimensional network structure.




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Bis[benzyl 2-(heptan-4-yl­idene)hydrazine-1-carboxyl­ate]bis­(thio­cyanato)­cobalt(II)

The title compound, [Co(NCS)2(C15H22N2O2)2] or C32H44CoN6O4S2, was prepared from cobalt(II) nitrate, benzyl carbazate and ammonium thio­cyanate in the presence of 4-hepta­none. The compound crystallizes with two centrosymmetric complexes in which the cobalt(II) atoms have a trans-CoO2N4 octa­hedral coordination geometry. In the crystal, N—H⋯S, C—H⋯S and C—H⋯.π contacts stack the complex mol­ecules along the b-axis direction.




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Di­bromido­[N-(1-di­ethyl­amino-1-oxo-3-phenyl­propan-2-yl)-N'-(pyridin-2-yl)imidazol-2-yl­idene]palladium(II) di­chloro­methane monosolvate

In the mol­ecule of the title N,N'-disubstituted imidazol-2-yl­idene palladium(II) complex, [PdBr2(C21H24N4O)]·CH2Cl2, the palladium(II) atom adopts a slightly distorted square-planar coordination (r.m.s. deviation = 0.0145 Å), and the five-membered chelate ring is almost planar [maximum displacement = 0.015 (8) Å]. The mol­ecular conformation is enforced by intra­molecular C—H⋯Br hydrogen bonds. In the crystal, complex mol­ecules and di­chloro­methane mol­ecules are linked into a three-dimensional network by C—H⋯O and C—H⋯Br hydrogen bonds.




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(1,4,8,11-Tetra­aza­cyclo­tetra­deca­ne)palladium(II) diiodide monohydrate

In the title compound, [Pd(C10H24N4)]I2·H2O, the PdII ion is four-coordinated in a slightly distorted square-planar coordination environment defined by four N atoms from a 1,4,8,11-tetra­aza­cyclo­tetra­decane ligand. The cationic complex, two I− anions and the solvent water mol­ecule are linked through inter­molecular hydrogen bonds into a three-dimensional network structure.




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Crystal structure of a salt with a protonated sugar cation and a cobalt(II) complex anion: (GlcN–H, K)[Co(NCS)4]·2H2O

The title compound, d-(+)-glucosa­mmonium potassium tetra­thio­cyanato­cobaltate(II) dihydrate, K(C6H14NO5)[Co(NCS)4]·2H2O or (GlcNH)(K)[Co(NCS)4]·2H2O, has been obtained as a side product of an incomplete salt metathesis reaction of d-(+)-glucosa­mine hydro­chloride (GlcN·HCl) and K2[Co(NCS)4]. The asymmetric unit contains a d-(+)-glucos­ammonium cation, a potassium cation, a tetra­iso­thio­cyanato­cobalt(II) complex anion and two water mol­ecules. The water mol­ecules coordinate to the potassium cation, which is further coordinated via three short K+⋯SCN− contacts involving three [Co(NCS)4]2− complex anions and via three O atoms of two d-(+)-glucosa­mmonium cations, leading to an overall eightfold coordination around the potassium cation. Hydrogen-bonding inter­actions between the building blocks consolidate the three-dimensional arrangement.




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1:1 Co-crystal of 3-ethyl-4-methyl-3-pyrrolin-2-one and 3-ethyl-4-methyl-3-pyrroline-2,5-dione

Crystallization from a 20-year-old commercial source of 3-ethyl-4-methyl-3-pyrrolin-2-one afforded 1:1 co-crystals of this compound (C7H11NO) with its oxidized derivative, 3-ethyl-4-methyl-3-pyrroline-2,5-dione (C7H9NO2). The compound crystallizes in the space group Poverline{1}, with two mol­ecules of each species in the asymmetric unit. These four mol­ecules form a hydrogen-bonded tetra­mer with a dimer of 3-ethyl-4-methyl-3-pyrrolin-2-one as the core flanked by one mol­ecule of the dione on each side.




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Synthesis and crystal structure of [Cs([2.2.2]crypt)]2[Mo(CO)5]

Reduction of the heteroleptic metal carbonyl complex Mo(CO)3(η5-Cp)H with the metallic salt Cs5Bi4 in the presence of [2.2.2]crypt (= 4,7,13,16,21,24-hexa­oxa-1,10-di­aza­bicyclo­[8.8.8]hexa­cosa­ne) in liquid ammonia led to single crystals of bis­[(4,7,13,16,21,24-hexa­oxa-1,10-di­aza­bicyclo­[8.8.8]hexa­cosa­ne)caesium] penta­carbonyl­molybdate, [Cs(C18H36N2O6)]2[Mo(CO)5] or [Cs([2.2.2]crypt)]2[Mo(CO)5]. The twofold negatively charged anionic complex corresponds to the 18 valence electron rule. It consists of an Mo atom coordinated by five carbonyl ligands in a shape inter­mediate between trigonal–bipyramidal and square-pyramidal. The Mo—C distances range from 1.961 (3) to 2.017 (3) Å, and the C≡O distances from 1.164 (3) to 1.180 (4) Å.




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(E)-1-(2-Hy­droxy-6-meth­oxy­phen­yl)-3-(2-meth­oxy­naphthalen-1-yl)prop-2-en-1-one

In the title compound, C21H18O4, the dihedral angle between the naphthelene ring system (r.m.s. deviation = 0.014 Å) and the benzene ring is 9.68 (1)°. The C atom of the meth­oxy group of the naphthalene ring system is almost coplanar with the ring [C—O—C—C = −2.0 (3)°], whereas the C atom of the meth­oxy group of the phenol ring is slightly twisted [C—O—C—C = 6.2 (3)°]. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif.




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4-Amino-5-{[cyclo­hex­yl(meth­yl)amino]­meth­yl}iso­phthalo­nitrile

The title compound, C16H20N4, was synthesized by cyanation of brom­hexine. The compound crystallizes with two unique mol­ecules in the asymmetric unit. The substituted aniline and cyclo­hexane rings are inclined to one another by 37.26 (6)° in one mol­ecule and by 22.84 (7)° in the other. In the crystal packing, intra- and inter­molecular N—H⋯N hydrogen bonds and an inter­molecular C—H⋯N contact were observed.




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2-[(1-Benzyl-1H-1,2,3-triazol-4-yl)meth­oxy]-1-naphthaldehyde

In the title compound, C21H17N3O2, the triazole ring system is inclined at dihedral angles of 4.14 (18) and 69.24 (11)° with the naphthalene ring system and phenyl ring, respectively. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds into double columns propagating along the b-axis direction.