RIKEN structural genomics beamlines at SPring-8

RIKEN structural genomics beamlines at the SPring-8; high throughput protein crystallography with automated beamline operation

RIKEN Structural Genomics Beamlines, BL26B1 & BL26B2 at the SPring-8, have been constructed for the structural genomics research. The main feature of the beamline is full automation of the successive data collections to maximize the beam-time efficiency. The beamline optics adopted a standard design commonly used for the SPring-8 bending magnet beamlines. Beamline instruments are operated by centralized control system through the computer network to achieve the automatic operation. The core part of the beamline development is a sample management system composed of sample changer robots for laboratory and beamline, and a networked sample database. BL26B1 has started user operation, and the automatic operation with the sample management system has been implemented at BL26B2.

Crystal structure of the conserved protein TTHA0727 from Thermus thermophilus HB8 at 1.9 A resolution: A CMD family member distinct from carboxymuconolactone decarboxylase (CMD) and AhpD

TTHA0727 is a conserved hypothetical protein from Thermus thermophilus HB8, with a molecular mass of 12.6 kDa. TTHA0727 belongs to the carboxymuconolactone decarboxylase (CMD) family (Pfam 02627). A sequence comparison with its homologs suggested that TTHA0727 is a distinct protein from alkylhydroperoxidase AhpD and gamma-carboxymuconolactone decarboxylase in the CMD family. Here we report the 1.9 A crystal structure of TTHA0727 (PDB ID: 2CWQ) determined by the multiwavelength anomalous dispersion method. The TTHA0727 monomer structure consists of seven alpha-helices (alpha1-alpha7) and one short 3(10)-helix. The crystal structure and the analytical ultracentrifugation revealed that TTHA0727 forms a hexameric ring structure in solution. The electrostatic potential distribution on the solvent-accessible surface of the TTHA0727 hexamer showed that positively charged regions exist on the side of the ring structure, suggesting that TTHA0727 interacts with some negatively charged molecules. A structural homology search revealed that the structure of three alpha-helices (alpha4-alpha6) is remarkably conserved, suggesting that it is the common structural motif for the CMD family proteins. In addition, the nine residues of the N-terminal tag bound to the cleft region between alpha1 and alpha3 in chains A and B of TTHA0727, implying that this region is the putative binding/active site for some small molecules.

Crystal structure of an enhancer of rudimentary homolog (ERH) at 2.1 Angstroms resolution

The enhancer of rudimentary gene, e(r), of Drosophila melanogaster encodes an enhancer of rudimentary (ER) protein with functions implicated in pyrimidine biosynthesis and the cell cycle. The ER homolog (ERH) is highly conserved among vertebrates, invertebrates, and plants. Xenopus laevis ERH was reported to be a transcriptional repressor. Here we report the 2.1 Angstroms crystal structure of murine ERH (Protein Data Bank ID 1WZ7), determined by the multiwavelength anomalous dispersion (MAD) method. The monomeric structure of ERH comprises a single domain consisting of three alpha-helices and four beta-strands, which is a novel fold. In the crystal structure, ERH assumes a dimeric structure, through interactions between the beta-sheet regions. The formation of an ERH dimer is consistent with the results of analytical ultracentrifugation. The residues at the core region and at the dimer interface are highly conserved, suggesting the conservation of the dimer formation as well as the monomer fold. The long flexible loop (44 approximately 53) is also significantly conserved, suggesting that this loop region may be important for the functions of ERH. In addition, the putative phosphorylation sites are located at the start of the beta2-strand (Thr18) and at the start of the alpha1-helix (Ser24), implying that the phosphorylation might cause some structural changes.

Crystal structure of ribosomal protein L27 from Thermus thermophilus HB8

Ribosomal protein L27 is located near the peptidyltransferase center at the interface of ribosomal subunits, and is important for ribosomal assembly and function. We report the crystal structure of ribosomal protein L27 from Thermus thermophilus HB8, which was determined by the multiwavelength anomalous dispersion method and refined to an R-factor of 19.7% (R(free) = 23.6%) at 2.8 A resolution. The overall fold is an all beta-sheet hybrid. It consists of two sets of four-stranded beta-sheets formed around a well-defined hydrophobic core, with a highly positive charge on the protein surface. The structure of ribosomal protein L27 from T. thermophilus HB8 in the RNA-free form is investigated, and its functional roles in the ribosomal subunit are discussed.