Crystal structure of head-to-head dimers of cholic and deoxycholic acid derivatives with different symmetric bridges

The crystal structure of three head-to-head dimers (having two cholic acid or deoxycholic acid units) linked at carbon atoms C3 by aromatic or alkyl bridges is studied. An internal coordinates system is necessary for describing the relative orientation in the space of the two bile acid residues. Five angles (three torsion and two common ones) are necessary for defining the relative position of both steroid residues in space. Carbon atoms C3 (which always carries a α-hydroxy group in natural bile acids), and C10 and C13 (which always carry β-methyl groups) of each steroid residue are suitable for this purpose. Furthermore, the distance between each C3 carbon atoms of both steroid residues will allow one to locate the steroids in space. The three dimers selected provide a large range of values for these angles. The packing, hydrogen bond network, and location of guest in the three crystals are discussed.     

Investigation of telomere length dynamics in induced pluripotent stem cells using quantitative fluorescence in situ hybridization

Here we attempted to clarify telomere metabolism in parental cells and their derived clonal human induced pluripotent stem cells (iPSCs) at different passages using quantitative fluorescence in situ hybridization (Q-FISH). Our methodology involved estimation of the individual telomere lengths of chromosomal arms in individual cells within each clone in relation to telomere fluorescence units (TFUs) determined by Q-FISH. TFUs were very variable within the same metaphase spread and within the same cell. TFUs of the established iPSCs derived from human amnion (hAM933 iPSCs), expressed as mean values of the median TFUs of 20 karyotypes, were significantly longer than those of the parental cells, although the telomere extension rates varied quite significantly among the clones. Twenty metaphase spreads from hAM933 iPSCs demonstrated no chromosomal instability. The iPSCs established from fetal lung fibroblasts (MRC-5) did not exhibit telomere shortening and chromosomal instability as the number of passages increased. However, the telomeres of other iPSCs derived from MRC-5 became shorter as the number of passages increased, and one (5%) of 20 metaphase spreads showed chromosomal abnormalities including X trisomy at an early stage and all 20 showed abnormalities including X and 12 trisomies at the late stage.     

Serine/threonine kinases and E2-ubiquitin conjugating enzymes in Planctomycetes: unexpected findings

The regulation of signal transduction by phosphorylation and ubiquitination is essential to ensure the correct behavior of eukaryotic cells. We searched for protein families involved in such signaling in several eukaryotic species and in a limited set of prokaryotes, where two members of the Planctomycetes phylum were included as they exhibit eukaryote-like features (Gemmata obscuriglobus and Pirellula staleyi). We identified sequences homologous to eukaryotic serine/threonine kinases (STKs) and E2-ubiquitin conjugating enzymes in the two Planctomycetes species. To extend these analyses to the Planctomycetes/Verrucomicrobia/Chlamydia super-phylum, we performed comparative analyses using domains from kinases, phosphatases and GTPases that serve as signaling signatures, and we analyzed their distributions. We found substantial differences in kinome densities with regards to other prokaryote clades and among the groups in the Planctomycetes/Verrucomicrobia/Chlamydia super-phylum. In addition, we identified the presence of classic eukaryotic E2-conjugating ubiquitin proteins in prokaryotes, these having previously believed to exist only in eukaryotes. Our phylogenetic analyses of the STKs signature domains and E2-enzymes suggest the existence of horizontal gene transfer.     

Purification and Properties of a New l-Fucose-specific Lectin Produced by Streptomyces No. 100–2

The inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamide derivatives on human 5-lipoxygenase (5-LO), a key enzyme in arachidonic acid cascades, were examined using 5-LO produced by Escherichia coli. Some of the tested compounds inhibited the conversion of arachidonic acid to 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE), and in particular the N-phenylbutyl derivative was about 30 times more active (IC₅₀ = 35 μm) than caffeic acid (IC₅₀ = 1000 μm), a known selective 5-LO inhibitor.     

Human Erythrocyte Receptor of l-Fucose-specific Lectin Produced by Streptomyces sp.

L-Fucose-specific lectin produced by Streptomyces no. 16-3 (SFL 16-3) was labeled with N- succinimidyl-[2, 3-³H]-propionate to quantitatively investigate its binding to human erythrocytes. The binding inhibition by sugars was competitive, and 5mM L-fucose or 20 mM d-mannose completely inhibited the binding. Among plant lectins, Lotus tetragonolobus, Ulex europeus I, soybean and wheat germ lectin showed competitive inhibition. The association constant and the average number of binding sites for human blood group O erythrocytes were approximately 3 × 10⁷ M^-1 and 1 × 10⁶ cell^-1, respectively. Trypsinization of erythrocytes preferentially increased the number of binding sites for human A and B erythrocytes but not for O erythrocytes.

Membrane components were extracted from human B and O erythrocytes and their binding activity for SFL 16-3 was tested using the hemagglutination-inhibition assay. Poly(glycosyl)-ceramide was the predominant receptor and its fucosyl residue was essential for binding. The crude glycoprotein fraction showed only slight inhibition activity.     

Sugar Specificity in the Induction and on the Activity of Streptomyces α-d-Galactosidases

The α-d-galactosidases of six Streptomyces strains were examined on their inducer susceptibility, substate specificity, and inhibitor susceptibility. In all strains examined, α-d-galactosidase was induced by d-galactose, but neither by d-fucose nor by l-arabinose. α-d-Fucosidase activity was always induced accompanying with α-d-galactosedase activity. β-l-Arabinosidase activity, however, was never observed. These α-d-galactosidases were purified to electrophoretically pure degree by successive ammonium sulfate and ethanol precipitation, and ion exchange and gel filtration chromatography. The purified preparations from six strains were different from each other in their chromatographic behaviors and in some physical properties, but they all showed strong α-d-fucosidase activity as well. The α-d-galactosidase activities were strongly inhibited by d-galactose and l-arabinose, but scarcely by d-fucose. On the other hand, their α-d-fucosidase activities were inhibited by d-fucose as well as by d-galactose and l-arabinose.     

l-Sorbose Oxidase from Trametes sanguinea

A crude inhibitor for pancreatic lipase was extracted from soybean seeds. The lipase activity decreased curvilinearly with an increase in inhibitor concentration. At a low inhibitor concentration, enhanced inhibition was observed by the co-existence of protein such as bovine serum albumin in the reaction mixture. The lipase activity was inhibited immediately after the addition of inhibitor which did not cause the significant destraction of substrate emulsion. The lipase activities of Aspergillus niger, Rhizopus delemar and castor bean seeds were also inhibited. The inhibition was observed when various oil substrates such as soybean oil, linseed oil, olive oil emulsions and Ediol were used, and the extent of inhibition varied among them. Column chromatography of inhibitor on Sephadex G–100 showed that the molecular weight of a main peak of inhibitor was estimated as about 80,000.     

The daidzein- and estradiol- induced anorectic action in CCK or leptin receptor deficiency rats

We investigated the effect of daidzein feeding and estradiol treatment on food intake in cholecystokinin-1 receptor (CCK1R) deficiency, leptin receptor (ObRb) deficiency rats and their wild-type rats. These rats underwent an ovariectomy or a sham operation. For the 5 week experiment, each rat was divided in three groups: control, daidzein (150 mg/kg diet), and estradiol (4.2 μg/rat/day) groups. In both CCK1R+ and CCK1R? rats, daidzein feeding and estradiol treatment significantly decreased food intake. Daidzein feeding significantly reduced food intake in ovariectomized ObRb? rats, although not in ObRb+ rats. Estradiol treatment significantly lowered food intake in ovariectomized ObRb+ and ObRb? rats. In the ovariectomized rats, estradiol treatment significantly increases uterine weight, while daidzein feeding did not change it, suggesting that daidzein might have no or weak estrogenic effect in our experiment. These results suggest that CCK1R and ObRb signalings were not essential for the daidzein- and estradiol-induced anorectic action.