Structural insights into Xanthomonas campestris pv. campestris NAD+ biosynthesis via the NAM salvage pathway.

Nicotinamide phosphoribosyltransferase (NAMPT) plays an important role in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) via the nicotinamide (NAM) salvage pathway. While the structural biochemistry of eukaryote NAMPT has been well studied, the catalysis mechanism of prokaryote NAMPT at the molecular level remains largely unclear. Here, we demonstrated the NAMPT-mediated salvage pathway is functional in the Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) for the synthesis of NAD+, and the enzyme activity of NAMPT in this bacterium is significantly higher than that of human NAMPT in vitro. Our structural analyses of Xcc NAMPT, both in isolation and in complex with either the substrate NAM or the product nicotinamide mononucleotide (NMN), uncovered significant details of substrate recognition. Specifically, we revealed the presence of a NAM binding tunnel that connects the active site, and this tunnel is essential for both catalysis and inhibitor binding. We further demonstrated that NAM binding in the tunnel has a positive cooperative effect with NAM binding in the catalytic site. Additionally, we discovered that phosphorylation of the His residue at position 229 enhances the substrate binding affinity of Xcc NAMPT and is important for its catalytic activity. This work reveals the importance of NAMPT in bacterial NAD+ synthesis and provides insights into the substrate recognition and the catalytic mechanism of bacterial type II phosphoribosyltransferases.

Crystal structure of transcription factor TGA7 from Arabidopsis.

TGA family of transcription factors play important roles in the systemic acquired resistance (SAR) in plants. In SAR, TGA7 binds to the activation sequence-1 (as-1) in the promoter region of SAR related genes and regulates their expressions in an NPR1 dependent manner. Despite its important roles in plant immunity, the molecular mechanism for DNA binding of TGA7 remains unclear. In the present work, we resolved the crystal structure of TGA7 dimers at a resolution of 2.06 Å, in which each monomer binds one molecule of palmitate. Further biochemical studies revealed that TGA7 specifically binds to the TGACG boxes of as-1 DNA in the form of homodimers, and it has specific requirements for the relative spacing and orientation of the two TGACG boxes. Moreover, we built a TGA7-DNA complex model and confirmed by site-directed mutagenesis that amino acid residue R109 in the DNA binding domain (DBD) of TGA7 is a key residue responsible for DNA recognition. Our work offers a good example for structural and functional studies of TGA proteins, and provides key clues to understand the DNA binding mechanism of TGA proteins in the SAR.

Sustainable Self-Cleaning Evaporators for Highly Efficient Solar Desalination Using a Highly Elastic Sponge-like Hydrogel.

Interfacial evaporation using light-absorbing hydrogels offers efficient solar evaporation performance under natural sunlight, ensuring an affordable clean water supply. However, achieving light-absorbing hydrogels with durable and efficient utilization is still a challenge due to inevitable salt accumulation, a difficult-to-control surface morphology, and poor mechanical properties on the surfaces of hydrogel-based evaporators. In this work, a photothermal sponge-like hydrogel with a 3D interconnected porous structure was constructed using low-cost activated carbon as a photothermal material, as well as a double-network polymer chain as the basic skeleton using a simple foaming polymerization strategy. The sponge-like hydrogel evaporator showed tailored surface topography, adequate water transport, excellent elasticity and toughness, good salt rejection, and thermal localization properties. Under the irradiation of simulated sunlight (1.0 kW/m2), a high evaporation rate of 2.33 kg·m-2·h-1 was achieved. Furthermore, efficient salt self-cleaning behavior was achieved due to the fast ion diffusion within the 3D interconnected porous structures. Even in highly concentrated brine of 15 wt %, continuous and efficient water evaporation was still achieved. The excellent evaporation and salt rejection properties of this photothermal sponge-like hydrogel indicated its promising long-term sustainable utilization in seawater desalination.

Discovery of (2-(pyrrolidin-1-yl)thieno[3,2-d]pyrimidin-4-yl)(3,4,5-trimethoxyphenyl)methanone as a novel potent tubulin depolymerizing and vascular disrupting agent.

In this study, a series of 2-substituted thieno[3,2-d]pyrimidin-4-yl(3,4,5-trimethoxyphenyl)methanones were designed, synthesized and evaluated as novel anti-tubulin polymerization and vascular disrupting agents. A pyrrolidin-1-yl derivative, compound 20, exhibited strong antiproliferative activities (average IC50 = 13.4 nM) against four cancer cell lines. 20 also showed retained potency toward paclitaxel-resistant A549 cells. 20 could significantly inhibit tubulin polymerization with an IC50 of 1.6 µM. 20 displayed strong induction of G2/M arrest and apoptosis through the mitochondrial pathway. Dose-dependent suppression of the migration of cancer cells and the formation of a vascular network were observed after treatment with 20. The acceptable microsomal stability implied that it is worth conducting further study on the analogues of 20 as novel drug candidates of CBSIs.

Design, synthesis, and biological evaluation of (e)-3,4-dihydroxystyryl aralkyl sulfones and sulfoxides as novel multifunctional neuroprotective agents.

Novel (E)-3,4-dihydroxystyryl aralkyl sulfones and sulfoxides were designed and synthesized as new analogues of 1, which showed interesting multifunctional neuroprotective effects, including antioxidative and antineuroinflammatory properties. Specifically, target compounds display excellent potency in scavenging reactive free radicals and demonstrate potent effects against various kinds of toxicities, including H2O2, 6-hydroxydopamine, and lipopolysaccharide in different types of neuronal cells. The antioxidative properties of the target compounds are more potent than that of 1, and the antineuroinflammatory properties are less strong than that of 1. According to the parallel artificial membrane permeation assay for the blood-brain barrier, target compounds possess greater blood-brain barrier (BBB) permeability than 1. In short, due to improvement of the antioxidative effect, stability, and BBB permeability, (E)-3,4-dihydroxystyryl aralkyl sulfones and sulfoxides can thus be considered as potential multifunctional neuroprotective agents and serve as new lead candidates in the treatment of neurodegenerative diseases.