Acta Crystallographica Section F-structural Biology and Crystallization Communications最新文献

Two-component and phosphorelay signal-transduction proteins are crucial for bacterial cell-cycle regulation in Caulobacter crescentus. ChpT is an essential histidine phosphotransferase that controls the activity of the master cell-cycle regulator CtrA by phosphorylation. Here, the 2.2 Å resolution crystal structure of ChpT is reported. ChpT is a homodimer and adopts the domain architecture of the intracellular part of class I histidine kinases. Each subunit consists of two distinct domains: an N-terminal helical hairpin domain and a C-terminal α/β domain. The two N-terminal domains are adjacent within the dimer, forming a four-helix bundle. The ChpT C-terminal domain adopts an atypical Bergerat ATP-binding fold.

Crustacean crustacyanin proteins are linked to the production and modification of carapace colour, with direct implications for fitness and survival. Here, the structural and functional properties of the two recombinant crustacyanin subunits H(1) and H(2) from the American lobster Homarus americanus are reported. The two subunits are structurally highly similar to the corresponding natural apo crustacyanin CRTC and CRTA subunits from the European lobster H. gammarus. Reconstitution studies of the recombinant crustacyanin proteins H(1) and H(2) with astaxanthin reproduced the bathochromic shift of 85-95 nm typical of the natural crustacyanin subunits from H. gammarus in complex with astaxanthin. Moreover, correlations between the presence of crustacyanin genes in crustacean species and the resulting carapace colours with the spectral properties of the subunits in complex with astaxanthin confirmed this genotype-phenotype linkage.

As-p18 is a fatty-acid-binding protein from the parasitic nematode Ascaris suum. Although it exhibits sequence similarity to mammalian intracellular fatty-acid-binding proteins, it contains features that are unique to nematodes. Crystals were obtained, but initial diffraction data analysis revealed that they were composed of a number of `microdomains'. Interpretable data could only be collected using a microfocus beamline with a beam size of 12 × 8 µm.

Human arginase I (HAI) is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of L-arginine to form L-ornithine and urea through a metal-activated hydroxide mechanism. Since HAI regulates L-Arg bioavailability for NO biosynthesis, it is a potential drug target for the treatment of cardiovascular diseases such as atherosclerosis. X-ray crystal structures are now reported of the complexes of Mn(2)(2+)-HAI and Co(2)(2+)-HAI with L-2-amino-3-guanidinopropionic acid (AGPA; also known as dinor-L-arginine), an amino acid bearing a guanidinium side chain two methylene groups shorter than that of L-arginine. Hydrogen bonds to the α-carboxylate and α-amino groups of AGPA dominate enzyme-inhibitor recognition; the guanidinium group does not interact directly with the metal ions.

Histidine triad nucleotide-binding protein 1 (HINT1) represents the most ancient and widespread branch of the histidine triad protein superfamily. HINT1 plays an important role in various biological processes and has been found in many species. Here, the structure of the human HINT1-adenosine 5'-monophosphate (AMP) complex at 1.38 Å resolution obtained from a new monoclinic crystal form is reported. The final structure has R(cryst) = 0.1207 (R(free) = 0.1615) and the model exhibits good stereochemical quality. Detailed analysis of the high-resolution data allowed the details of the protein structure to be updated in comparison to the previously published data.

Prodigiosin, which is a member of the prodiginines, is a red linear tripyrrole compound. A gene cluster for the biosynthesis of prodigiosin has been identified in Serratia and most genes in the cluster have been functionally assigned. A bifurcated biosynthetic pathway for prodigiosin has previously been determined. The last step in the biosynthetic pathway of 4-methoxy-2,2'-bipyrrole-5-carbaldehyde (MBC) is catalyzed by PigF, which transfers a methyl group to 4-hydroxy-2,2'-bipyrrole-5-carbaldehyde (HBC) to form the terminal product MBC, but its catalytic mechanism is not known. To elucidate its mechanism, recombinant PigF was purified and crystallized. The crystals belonged to space group P2(1), with unit-cell parameters a = 69.4, b = 52.4, c = 279.2 Å, β = 96.8°. The native crystals may contain six molecules in the asymmetric unit, with a V(M) of 2.17 Å(3) Da(-1) and a solvent content of 43.43%. A full data set was collected at 2.6 Å resolution using synchrotron radiation on beamline BL17U of Shanghai Synchrotron Radiation Facility (SSRF), People's Republic of China. Molecular replacement was unsuccessful. To solve the structure of PigF by experimental phasing, selenomethionine-derivativized protein crystals were prepared from a condition with 0.01 M spermidine as an additive. One crystal diffracted to 1.9 Å resolution and a full data set was collected on beamline BL17U at SSRF. The crystal belonged to space group P2(1), with unit-cell parameters a = 69.0, b = 52.9, c = 93.4 Å, β = 97.3°. Heavy-atom substructure determination and phasing by SAD clearly showed that the crystal contains two molecules in the asymmetric unit, with a V(M) of 2.19 Å(3) Da(-1) and a solvent content of 43.82%.

Magnetosomes in magnetotactic bacteria have been widely used in studies of magnetic domains and in commercial applications. The iron content of magnetotactic bacteria is ∼100 times higher than that of Escherichia coli. Magnetospirillum gryphiswaldense MSR-1 can still take up iron even at high intracellular concentrations. Ferric uptake regulator (Fur) is a global iron-responsive regulator that affects magnetosome formation, iron transport and oxygen metabolism. However, the mechanism of iron uptake and homeostasis by M. gryphiswaldense MSR-1 Fur is not clear. Here, the expression, purification and crystallization of apo and SeMet Fur from M. gryphiswaldense MSR-1 are reported. The crystals belonged to space group C2. Matthews coefficient analysis and size-exclusion chromatography showed that the asymmetric unit probably contains one dimer of Fur. Diffraction data were optimized to 1.58 Å resolution for apo Fur and to 1.9 Å resolution for SeMet Fur.

The ribosome-dependent mRNA interferase YafO from Escherichia coli belongs to a type II toxin-antitoxin (TA) system and its cognate antitoxin YafN neutralizes cell toxicity by forming a stable YafN-YafO complex. The YafN-YafO TA system is upregulated by the SOS response (a global response to DNA damage in which the cell cycle is arrested and mutagenesis is induced) and may then inhibit protein synthesis by endoribonuclease activity of YafO with the 50S ribosome subunit. Structural information on the YafN-YafO complex and related complexes would be helpful in order to understand the structural basis of the mechanism of mRNA recognition and cleavage, and the assembly of these complexes. Here, the YafN-YafO complex was expressed and crystallized. Crystals grown by the hanging-drop vapour-diffusion method diffracted to 3.50 Å resolution and belonged to the hexagonal space group P622, with unit-cell parameters a = 86.14, b = 86.14, c = 173.11 Å, α = β = 90, γ = 120°. Both Matthews coefficient analysis and the self-rotation function suggested the presence of one molecule per asymmetric unit in the crystal, with a solvent content of 65.69% (V(M) = 3.58 Å(3) Da(-1)).

With its ability to show the interactions between drug-target proteins and small-molecule ligands, X-ray crystallography is an essential tool in drug-discovery programmes. However, its usefulness can be limited by crystallization artifacts or by the data resolution, and in particular when assumptions of unimodal binding (and isotropic motion) do not apply. Discrepancies between the modelled crystal structure and the physiological range of structures generally prevent quantitative estimation of binding energies. Improved crystal structure resolution will often not aid energy estimation because the conditions which provide the highest rigidity and resolution are not likely to reflect physiological conditions. Instead, strategies must be employed to measure and model flexibility and multiple binding modes to supplement crystallographic information. One useful tool is the use of anomalous dispersion for small molecules that contain suitable atoms. Here, an analysis of the binding of the kinase inhibitor H-89 to protein kinase A (PKA) is presented. H-89 contains a bromobenzene moiety that apparently binds with multiple conformations in the kinase ATP pocket. Using anomalous dispersion methods, it was possible to resolve these conformations into two distinct binding geometries.

The innate immune response is the first defence system against pathogenic microorganisms, and cytosolic detection of pathogen-derived DNA is believed to be one of the major mechanisms of interferon production. Recently, the mammalian ER membrane protein STING (stimulator of IFN genes; also known as MITA, ERIS, MPYS and TMEM173) has been found to be the master regulator linking the detection of cytosolic DNA to TANK-binding kinase 1 (TBK1) and its downstream transcription factor IFN regulatory factor 3 (IRF3). In addition, STING itself was soon discovered to be a direct sensor of bacterial cyclic dinucleotides such as c-di-GMP or c-di-AMP. However, structural studies of apo STING and its complexes with these cyclic dinucleotides and with other cognate binding proteins are essential in order to fully understand the roles played by STING in these crucial signalling pathways. In this manuscript, the successful crystallization of the C-terminal domain of murine STING (STING-CTD; residues 138-344) is reported. Native and SeMet-labelled crystals were obtained and diffracted to moderate resolutions of 2.39 and 2.2 Å, respectively.