The cullin-RING ubiquitin ligases are multisubunit complexes that ubiquitinate various proteins. Six different cullins encoded by the human genome selectively pair with different adaptors and substrate receptors. It is presently poorly understood how cullin-2 (Cul2) and cullin-5 (Cul5) associate specifically with their adaptor elongin BC and a SOCS-box-containing substrate receptor. Here, crystallographic and mutational analyses of a quaternary complex between the N-terminal half of Cul5, elongin BC and SOCS2 are reported. Cul5 interacts extensively with elongin BC via residues that are highly conserved in Cul2 but not in other cullins. Cul5 also interacts with SOCS2, but via only two residues, Pro184 and Arg186, which are located in the C-terminal part of the SOCS box called the Cul5 box. Pro184 makes a ring-to-ring interaction with Trp53 of Cul5, which is substituted by alanine in Cul2. This interaction is shown to contribute significantly to the overall binding affinity between Cul5 and SOCS2-elongin BC. This study provides structural bases underlying the specificity of Cul5 and Cul2 for elongin BC and their preferential association with Cul5 or Cul2 box-containing substrate receptors.

In many prokaryotic organisms, chromosomal loci known as clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (CAS) genes comprise an acquired immune defense system against invading phages and plasmids. Although many different Cas protein families have been identified, the exact biochemical functions of most of their constituents remain to be determined. In this study, we report the crystal structure of PF1127, a Cas protein of Pyrococcus furiosus DSM 3638 that is composed of 480 amino acids and belongs to the Csx1 family. The C-terminal domain of PF1127 has a unique β-hairpin structure that protrudes out of an α-helix and contains several positively charged residues. We demonstrate that PF1127 binds double-stranded DNA and RNA and that this activity requires an intact β-hairpin and involve the homodimerization of the protein. In contrast, another Csx1 protein from Sulfolobus solfataricus P2 that is composed of 377 amino acids does not have the β-hairpin structure and exhibits no DNA-binding properties under the same experimental conditions. Notably, the C-terminal domain of these two Csx1 proteins is greatly diversified, in contrast to the conserved N-terminal domain, which appears to play a common role in the homodimerization of the protein. Thus, although P. furiosus Csx1 is identified as a nucleic acid-binding protein, other Csx1 proteins are predicted to exhibit different individual biochemical activities.

We report on a new surface modification method for grafting a "dynamic" property for on-demand activation of the click reaction. Our approach utilizes the acetylene group masked with dicobalt hexacarbonyl, Co(2)(CO)(6), which is not reactive toward the click reaction. Electrochemical treatment reveals the acetylene group on the selected region, which is then used as a chemical handle for surface functionalization via the click reaction with an azide-containing molecule. Electrochemical and chemical conversions on the surface were verified by cyclic voltammetry, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. We have demonstrated immobilization of an azide-modified RGD peptide and promotion of cell adhesion/migration to the region of electrochemical induction.

A novel process for transparent oxide ceramic scintillator with a composition of Gd1.94-x Yx Eu0.06O3 was developed. The process consists of a glycine–nitrate combustion synthesis of nano-sized starting powder and subsequent controlled sintering and annealing steps. The organic molecules remaining in the as-combusted powder were efficiently removed by the combined heat-treatment at vacuum and air atmospheres. Hot-pressed ceramic scintillators show transparent optical state and high light output. Transparent optical ceramic scintillator with a high content of Gd (up to 80 mol%) was fabricated by the process. The measured light output of Gd1.54Y0.4Eu0.06O3 ceramic scintillator was about two times higher that that of CdWO4 single crystal.

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