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The enzymatic degradation of semi‐cellulosic substrates has recently received immense attention. The enzyme endo‐1,4‐β‐xylanase is essential for the complete digestion of complex and heterogeneous hemicellulose. Here, the purification, crystallization and preliminary X‐ray free‐electron laser (XFEL) diffraction analysis of endo‐1,4‐β‐xylanase from the fungus Hypocrea virens (HviGH11) are reported. Codon‐optimized HviGH11 was overexpressed in Escherichia coli and spontaneously crystallized after His‐tag purification and concentration. Preliminary XFEL diffraction data were collected at the Pohang Accelerator Laboratory XFEL (PAL‐XFEL). A total of 1021 images containing Bragg peaks were obtained and indexed. The HviGH11 crystals belonged to the orthorhombic space group P212121, with unit‐cell parameters a = 43.80, b = 51.90, c = 94.90 Å. Using 956 diffraction patterns, the phasing problem was solved and an initial model structure of HviGH11 was obtained. [ABSTRACT FROM AUTHOR]

Sample delivery using injectors is widely used in serial crystallography (SX) and has significantly contributed to the determination of crystal structures at room temperature. However, sophisticated injector nozzle fabrication methods and sample delivery operations have made it difficult for ordinary users to access the SX research. Herein, a simple and easily accessible sample delivery method for SX experiments is introduced, that uses a viscous medium, commercially available syringe and syringe pump. The syringe containing the lysozyme crystals embedded in lipidic cubic phase (LCP) or polyacrylamide (PAM) delivery media was connected to a needle having an inner diameter of 168 µm, after which it was installed on a syringe pump. By driving the syringe pump, the syringe plunger was pushed and the crystal sample was delivered to the X‐ray beam position in a stable manner. Using this system, the room‐temperature crystal structures of lysozyme embedded in LCP and PAM at 1.56 Å and 1.75 Å, respectively, were determined. This straightforward syringe pump‐based sample delivery system can be utilized in SX. [ABSTRACT FROM AUTHOR]

Fluorescent proteins (FPs) possess a wide variety of spectral properties that make them of widespread interest as optical markers. These proteins can be applied as pH indicators or metal biosensors. The discovery and characterization of new fluorescent proteins is expected to further extend their application. Here, we report the spectral and structural analysis of a red fluorescent protein from Acropora digitifera (designated AdRed). This protein shows a tetrameric state and is red emitting, with excitation and emission maxima at 567 and 612 nm, respectively. Its crystal structure shows the tetrameric interface stabilized by hydrogen bonding and salt bridges. The electron density map of the chromophore, consisting of Asp66–Tyr67–Gly68, shows the decarboxylated side chain of Asp66. Ser223, located near the chromophore, has the role of bridging His202 and Glu221, and is part of the hydrogen bond network. Mutated AdRed with Cys148Ser reveals a blue shift in fluorescence excitation and emission. Our results provide insights into understanding the molecular function of AdRed and other FPs. PDB Code(s): 6AA7 [ABSTRACT FROM AUTHOR]

The multifarious injection chamber for molecular structure study (MICOSS) experimental system has been developed at the Pohang Accelerator Laboratory X‐ray Free‐Electron Laser for conducting serial femtosecond crystallography. This system comprises several instruments such as a dedicated sample chamber, sample injectors, sample environment diagnostic system and detector stage for convenient distance manipulation. Serial femtosecond crystallography experiments of lysozyme crystals have been conducted successfully. The diffraction peaks have reached to ∼1.8 Å resolution at the photon energy of 9.785 keV. [ABSTRACT FROM AUTHOR]

The Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) is a recently commissioned X-ray free-electron laser (XFEL) facility that provides intense ultrashort X-ray pulses based on the self-amplified spontaneous emission process. The nano-crystallography and coherent imaging (NCI) hutch with forward-scattering geometry is located at the hard X-ray beamline of the PAL-XFEL and provides opportunities to perform serial femtosecond crystallography and coherent X-ray diffraction imaging. To produce intense highdensity XFEL pulses at the interaction positions between the X-rays and various samples, a microfocusing Kirkpatrick--Baez (KB) mirror system that includes an ultra-precision manipulator has been developed. In this paper, the design of a KB mirror system that focuses the hard XFEL beam onto a fixed sample point of the NCI hutch, which is positioned along the hard XFEL beamline, is described. The focusing system produces a two-dimensional focusing beam at approximately 2 mm scale across the 2-11 keV photon energy range. XFEL pulses of 9.7 keVenergy were successfully focused onto an area of size 1.94 mm x 2.08 mm FWHM. [ABSTRACT FROM AUTHOR]

Abstract: The CRISPR system is an adaptive RNA-based microbial immune system against invasive genetic elements. CasB is an essential protein component in Type I-E Cascade. Here, we characterize CasB proteins from three different organisms as non-specific nucleic acid binding proteins. The Thermobifida fusca CasB crystal structure reveals conserved positive surface charges, which we show are important for its nucleic acid binding function. EM docking reveals that CasB dimerization aligns individual nucleic acid binding surfaces into a curved, elongated binding surface inside Type I-E Cascade, consistent with the putative functions of CasB in ds-DNA recruitment and crRNA–DNA duplex formation steps. Structured summary of protein interactions: TthCasB and TthCasB bind by x-ray crystallography (View interaction) TfuCasB1 and TfuCasB1 bind by molecular sieving (View Interaction: 1, 2) [Copyright &y& Elsevier]

Abstract: Creatine kinase is a member of the phosphagen kinase family, which catalyzes the reversible phosphoryl transfer reaction that occurs between ATP and creatine to produce ADP and phosphocreatine. Here, three structural aspects of human-brain-type-creatine-kinase (hBB-CK) were identified by X-ray crystallography: the ligand-free-form at 2.2Å; the ADP–Mg2+, nitrate, and creatine complex (transition-state-analogue complex; TSAC); and the ADP–Mg2+-complex at 2.0Å. The structures of ligand-bound hBB-CK revealed two different monomeric states in a single homodimer. One monomer is a closed form, either bound to TSAC or the ADP–Mg2+-complex, and the second monomer is an unliganded open form. These structural studies provide a detailed mechanism indicating that the binding of ADP–Mg2+ alone may trigger conformational changes in hBB-CK that were not observed with muscle-type-CK. [Copyright &y& Elsevier]

The protein encoded by the MJ0754 gene from the archaeon Methanococcus jannaschii DSM 2661 is an unknown hypothetical protein. Two recombinant proteins, MJ0754 (residues 1-185) and MJ0754t (a truncated form of MJ0754, residues 11-185), were cloned from MJ0754, overexpressed as His-tag fusion proteins and purified. The crystals were found to grow under two different conditions and to have two different shapes. The crystal of MJ0754 belonged to space group P61, with unit-cell parameters a = b = 127.015, c = 48.929 Å, a calculated Matthews coefficient of 2.85 Å3 Da−1 and two molecules per asymmetric unit. The crystal of MJ0754t belonged to space group C2221, with unit-cell parameters a = 51.915, b = 79.122, c = 93.869 Å, a calculated Matthews coefficient of 2.41 Å3 Da−1 and one molecule per asymmetric unit. The SeMet-labelled P61 crystal diffracted to a resolution of 3.1 Å, while the native C2221 crystal diffracted to 1.3 Å resolution. [ABSTRACT FROM AUTHOR]

Probable tRNA-modification GTPase (TrmE) is a guanine nucleotide-binding protein that is conserved between bacteria and humans. GTPase hydrolyzes GTP and plays a pivotal role in signalling pathways. In this study, TrmE from Staphylococcus aureus was overexpressed in Escherichia coli. The enzyme was found to crystallize at 295 K when ammonium sulfate was used as a precipitant. X-ray diffraction data were collected to 2.9 Å resolution from the crystallized enzyme using synchrotron radiation. The crystal was found to belong to the cubic space group I23, with unit-cell parameters a = b = c = 229.47 Å, α = β = γ = 90°. The crystal is likely to contain four monomers in the asymmetric unit, with a corresponding VM of 2.4 Å3 Da−1 and a solvent content of 50%. [ABSTRACT FROM AUTHOR]

The tRNA-specific adenosine deaminase from the pathogenic bacteria Streptococcus pyogenes (spTAD) has been overexpressed in Escherichia coli and crystallized in the presence of Zn2+ ion at 295 K using ammonium sulfate as a precipitant. Flash-cooled crystals of spTAD diffracted to 2.0 A using 30%(v/v) glycerol as a cryoprotectant. X-ray diffraction data have been collected to 2.0 A using synchrotron radiation. The crystal belongs to the tetragonal space group P4(2)2(1)2, with unit-cell parameters a = b = 81.042, c = 81.270 A. The asymmetric unit contains one subunit of spTAD, with a corresponding crystal volume per protein weight (VM) of 3.3 A3 Da(-1) and a solvent content of 62.7%.