D-Amino acid oxidase of Streptomyces coelicolor and the effect of D-amino acids on the bacterium

The homologous gene of D-amino acid oxidase (DAO) in prokaryotic organisms is predominantly found in a group of bacteria called the Actinobacteria. We have analyzed the DAO of the model actinomycete Streptomyces coelicolor and the effect of D-amino acids on this bacterium. When expressed in Escherichia coli, the translated product of the putative dao gene of this bacterium exhibited oxidase activity against neutral and basic D-amino acids, with a higher activity toward D-valine and D-isoleucine, but not to their corresponding L-amino acids. This substrate specificity was largely different from that of the DAO of the actinobacterium Arthrobacter protophormiae. The gene message and DAO activity were constitutively detected in S. coelicolor cells, and unlike eukaryotic DAOs, the presence of a D-amino acid did not significantly induce expression. The D-amino acids that were a good substrate for S. coelicolor DAO inhibited cell growth, delayed morphological development and affected cell morphology, but they did not inhibit biofilm formation. Disruption of the dao gene had no effect on the morphology and morphological development of S. coelicolor cells, the assimilation of D-valine or the sensitivity to growth inhibition by D-valine under the experimental conditions, showing that in this bacterium DAO does not play a significant role in either morphological development or the assimilation and detoxification of D-amino acids.     

Biochemical characterization of a thermostable β-1,3-xylanase from the hyperthermophilic eubacterium, Thermotoga neapolitana strain DSM 4359

The biochemical properties of a putative β-1,3-xylanase from the hyperthermophilic eubacterium Thermotoga neapolitana DSM 4359 were determined from a recombinant protein (TnXyn26A) expressed in Escherichia coli. This enzyme showed specific hydrolytic activity against β-1,3-xylan and released β-1,3-xylobiose and β-1,3-xylotriose as main products. It displayed maximum activity at 85 °C during a 10-min incubation, and its activity half-life was 23.9 h at 85 °C. Enzyme activity was stable in the pH range 3–10, with pH 6.5 being optimal. Enzyme activity was significantly inhibited by the presence of N-bromosuccinimide (NBS). The insoluble β-1,3-xylan K _m value was 10.35 mg/ml and the k _cat value was 588.24 s^?1. The observed high thermostability and catalytic efficiency of TnXyn26A is both industrially desirable and also aids an understanding of the chemistry of its hydrolytic reaction.     

BPG3 is a novel chloroplast protein that involves the greening of leaves and related to brassinosteroid signaling

Brassinosteroids are plant steroid hormones that regulate plant organs and chloroplast development. The detailed molecular mechanism for plant development by BR signaling is yet to be revealed, and many points regarding the relationship between BR signaling and chloroplast development remain unknown. We identify here the dominant mutant Brz-insensitive-pale green3-1D (bpg3-1D) from the Arabidopsis FOX lines that show reduced sensitivity to the chlorophyll accumulation promoted by the BR biosynthesis inhibitor, Brassinazole (Brz), in the light. BPG3 encodes a novel chloroplast protein that is evolutionally conserved in bacteria, algae, and higher plants. The expression of BPG3 was induced by light and Brz. The inhibition of electron transport in photosystem II of the chloroplasts was detected in bpg3-1D. These results suggest that BPG3 played an important role in regulating photosynthesis in the chloroplast under BR signaling.     

Distinction of cell types in Dicyema japonicum (phylum Dicyemida) by expression patterns of 16 genes

Dicyemids (phylum Dicyemida) are endoparasites, or endosymbionts, typically found in the renal sac of benthic cephalopod molluscs. The body organization of dicyemids is very simple, consisting of only 9 to 41 somatic cells. Dicyemids appear to have no differentiated tissues. Although categorization of somatic cells, to some types, is based on differences in the pattern of cilia and their position in the body, whether or not these cells are functionally different remains to be revealed. To provide insight into the functional differentiation, we performed whole mount in situ hybridization (WISH) to detect expression patterns of 16 genes, i.e., aquaglyceroporin, F-actin capping protein, aspartate aminotransferase, cathepsin-L-like cysteine peptidase, Ets domain-containing protein, glucose transporter, glucose-6-phosphate 1-dehydrogenase, glycine transporter, Hsp 70, Hsp 90, isocitrate dehydrogenase subunit alpha, Rad18, serine hydroxymethyltransferase, succinate-CoA ligase, valosin-containing protein, and 14-3-3 protein. In certain genes, regional specific expression patterns were observed among somatic cells of vermiform stages and infusoriform larvae of dicyemids. The WISH analyses also revealed that the Ets domain-containing protein and Rad18 are molecular markers for agametes.     

Discovery, synthesis, and structure-activity relationship of 6-aminomethyl-7,8-dihydronaphthalenes as human melanin-concentrating hormone receptor 1 antagonists

Human melanin-concentrating hormone receptor 1 (hMCHR1) antagonists are promising targets for obesity treatment. We identified the tetrahydronaphthalene derivative 1a with modest binding affinity for hMCHR1 by screening an in-house G protein-coupled receptor (GPCR) ligand library. We synthesized a series of 6-aminomethyl-5,6,7,8-tetrahydronaphthalenes and evaluated their activity as hMCHR1 antagonists. Modification of the biphenylcarbonylamino group revealed that the biphenyl moiety played a crucial role in the interaction of the antagonist with the receptor. The stereoselective effect of the chiral center on binding affinity generated the novel 6-aminomethyl-7,8-dihydronaphthalene scaffold without a chiral center. Optimization of the amino group led to the identification of a potent antagonist 2s (4'-fluoro-N-[6-(1-pyrrolidinylmethyl)-7,8-dihydro-2-naphthalenyl][1,1'-biphenyl]-4-carboxamide), which significantly inhibited the nocturnal food intake in rats after oral administration. Pharmacokinetic analysis confirmed that 2s had good oral bioavailability and brain penetrance. This antagonist appears to be a viable lead compound that can be used to develop a promising therapy for obesity.     

Effect of low dietary rubidium on plasma biochemical parameters and mineral levels in rats

The effects of low dietary rubidium on plasma biochemical parameters and mineral levels in tissues in rats were studied. Eighteen male Wistar rats, weighing about 40 g, were divided into two groups and fed the diets with or without supplemental rubidium (0.54 vs 8.12 mg/kg diet) for 11 wk. Compared to the rats fed the diet with supplemental rubidium, the animals fed the diet without rubidium supplementation had higher urea nitrogen in plasma; lower rubidium concentration in tissues; lower sodium in muscle; higher potassium in plasma, kidney and tibia, and lower potassium in testis; lower phosphorus in heart and spleen; lower calcium in spleen; higher magnesium in muscle and tibia; higher iron in muscle; lower zinc in plasma and testis; and lower copper in heart, liver, and spleen, and higher copper in kidney. These results suggest that rubidium concentration in tissues reflects rubidium intake, and that rubidium depletion affects mineral (sodium, potassium, phosphorus, calcium, magnesium, iron, zinc, and copper) status.     

A Panel of Radiation Hybrids Defining the 7q31-q32 Region of Human Chromosome 7

Mouse A9 cells containing human chromosome 7 tagged with pSV2neowere irradiated with X-rays and fused to A9 cells to isolateG418-resistant clones. From these clones, we selected radiationhybrids that contained 10–40 Mb of human DNA apparentlyat a single site of their genome by FISH analysis using humanrepetitive sequences as a probe. Then we made a panel of hybridsthat contained various fragments of the 7q31-q32 region andcover its entire region altogether by PCR with STS markers ofhuman chromosome 7. This panel is useful in chromosome transferexperiments since the dominant selective marker neo gene isattached to human DNA.