Transport of neutral, cationic and anionic amino acids by systems B, b, XAG, and ASC in swine small intestine

Amino acid influx across the brush border membrane of the intact pig ileal epithelium was studied. It was examine whether in addition to system B, systems ASC and b^o,+ were involved in transport of bipolar amino acids. The kinetics of interactions between lysine and leucine demonstrates that system b^o,+ is present and accessible also to -glutamine. -aspartate (K_1/2 0.3 mM) and -glutamate (K_i 0.5 mM) share a high affinity transporter with a maximum rate of 1.3 μmol cm⁻² h⁻¹, while only -glutamate with a K_1/2 of 14.4 mM uses a low affinity transporter with a maximum rate of 2.7 μmol cm⁻² h⁻¹, system ASC, against which serine has a K_i of 1.6 mM. In the presence of 100 mM lysine, -glutamine (A), leucine (B), and methionine (C) fulfilled the criteria of the ABC test for transport by one and the same transporter. However, serine inhibits not only transport of -glutamate but also of glutamine (K_i 0.5 mM), and -glutamate inhibits part of the transport of glutamine. The test does, therefore, only indicate that the three bipolar amino acids have similar affinities for transport by systems B and ASC. Further study of the function of system B must be carried out under full inhibition by lysine and glutamate.     

可改良棉粕蛋白的菌株选育及其发酵

棉粕蛋白质含量高达38％~50％,然而作为饲料其蛋白质品质较差,饲料利用率较低。为提高其蛋白质利用率,从自然界筛选出了能够高效降解棉粕大分子蛋白质的优良菌株4株,经生化与分子生物学试验鉴定为Bacillus subtilis(2株,编号为H1和H7),Bacillus cereus (1株,编号为H9)和Aspergillus niger (1株,编号为P1)。通过单菌及组合发酵实验比较发现:最适宜菌种组合为B. subtilis(H1)和A. niger (P1)。两菌株组合发酵后,棉粕TCA-NSI(三氯乙酸氮溶指数)提高了25.34%,小分子多肽含量提高了11%,游离必需氨基酸提高了24%,蛋白质的体外消化率由44.56%提高到了78.61%,明显高于其他菌种组合,研究结果表明其组合发酵可有效改良棉粕蛋白品质,显著提高棉粕蛋白的饲用价值。     

Cutoff variation induces different topological properties: A new discovery of amino acid network within protein

An increasing attention has been dedicated to the characterization of complex networks within the protein world. Before now most investigations about protein structures were only considered where the interactive cutoff distance R_c=5 or 7 Å. It is noteworthy that the length of peptide bond is about 1.5 Å, the length of hydrogen bond is about 3 Å, the range of London-van der Waals force is about 5 Å and the range of hydrophobic effect can reach to 12 Å in protein molecule. Present work reports a study on the topological properties of the amino acid network constructed by different interactions above. The results indicate that the small-world property of amino acid network constructed by the peptide and hydrogen bond, London-van der Waals force and the hydrophobic effect is strong, very strong and relatively weak, respectively. Besides, there exists a precise exponential relation C∝k^−0.5 at R_c=12 Å. It means that the amino acid network constructed by the hydrophobic effect tend to be hierarchical. Functional modules could be the cause for hierarchical modularity architecture in protein structures. This study on amino acid interactive network for different interactions facilitates the identification of binding sites which is strongly linked with protein function, and furthermore provides reasonable understanding of the underlying laws of evolution in genomics and proteomics.     

Bot fly parasitism of the red-backed vole: host survival,infection risk,and population growth

Parasites can play an important role in the dynamics of host populations, but empirical evidence remains sparse. We investigated the role of bot fly (Cuterebra spp.) parasitism in red-backed voles (Myodes gapperi) by first assessing the impacts of the parasite on the probability of vole survival under stressful conditions as well as on the reproductive activity of females. We then identified the main factors driving both the individual risk of infection and the abundance of bot flies inside red-backed voles. Finally, we evaluated the impacts of bot fly prevalence on the growth rate of vole populations between mid-July and mid-August. Thirty-six populations of red-backed voles were sampled in the boreal forest of Québec, Canada. The presence and the abundance of parasites in voles, two host life history traits (sex and body condition), three indices of habitat complexity (tree basal area, sapling basal area, coarse woody debris volume), and vole abundance were considered in models evaluating the effects of bot flies on host populations. We found that the probability of survival of red-backed voles in live traps decreased with bot fly infection. Both the individual risk of infection and the abundance of bot flies in red-backed voles were driven mainly by vole abundance rather than by the two host life history traits or the three variables of habitat complexity. Parasitism had population consequences: bot fly prevalence was linked to a decrease in short-term growth rate of vole populations over the summer. We found that bot flies have the potential to reduce survival of red-backed voles, an effect that may apply to large portions of populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Relationships between Population Size, Genetic Diversity and Fitness Components in the Rare Plant Dictamnus albus in Central Germany

An increasing number of studies support the hypothesis that smaller populations face a higher risk of extinction, and declining population sizes are therefore one of the focal points in plant conservation. In small populations, loss of genetic diversity is often related to reduced reproductive fitness. For the rare Dictamnus albus in Central Germany, an earlier study had already confirmed a significant correlation between population size and genetic diversity. In order to assess whether these variables correlate with fitness components, plant height; flower, fruit and seed production; and germination were studied in a total of 11 populations of different size. In the seven populations that were sampled over two consecutive years, differences among populations and among years were tested using a Two-Way ANOVA. Co-linearity among variables was assessed using principal component analysis (PCA), followed by calculating correlations between ordination axes and both population size and genetic diversity. Plant height and flower number were uncorrelated to the other variables and, together with germination, did not show any correlation to either population size or genetic diversity. However, both size and genetic diversity of populations correlated significantly with other PCA axes that reflected reproductive components such as fruit number, seed number, seed fruit ratio, and seed mass. Our results support the idea that reproduction is hampered in small populations and raise concerns over the loss of genetic diversity in D. albus.     

Self-assemblies of Rab- and Arf-family small GTPases on lipid bilayers in membrane tethering

Small GTPases of the Ras superfamily, which include Ras-, Rho-, Rab-, Arf-, and Ran-family isoforms, are generally known to function as a nucleotide-dependent molecular switch in eukaryotic cells. In the GTP-loaded forms, they selectively recruit their cognate interacting proteins or protein complexes, termed “effectors,” to the cytoplasmic face of subcellular membrane compartments, thereby switching on the downstream effector functions, which are vital for fundamental cellular events, such as cell proliferation, cytoskeletal organization, and intracellular membrane trafficking. Nevertheless, in addition to acting as the classic nucleotide-dependent switches for the effectors, recent studies have uncovered that small GTPases themselves can be self-assembled specifically into homo-dimers or higher-order oligomers on membranes, and these assembly processes are likely responsible for their physiological functions. This Review focuses particularly on the self-assembly processes of Rab- and Arf-family isoforms during membrane tethering, the most critical step to ensure the fidelity of membrane trafficking. A summary of the current experimental evidence for self-assemblies of Rab and Arf small GTPases on lipid bilayers in chemically defined reconstitution system is provided     

Identification of five small heat shock protein genes in Spodoptera frugiperda and expression analysis in response to different environmental stressors

Spodoptera frugiperda (J. E. Smith) is a highly adaptable polyphagous migratory pest in tropical and subtropical regions. Small heat shock proteins (sHsps) are molecular chaperones that play important roles in the adaptation to various environment stressors. The present study aimed to clarify the response mechanisms of S. frugiperda to various environmental stressors. We obtained five S. furcifera sHsp genes (SfsHsp21.3, SfsHsp20, SfsHsp20.1, SfsHsp19.3, and SfsHsp29) via cloning. The putative proteins encoded by these genes contained a typical α-crystallin domain. The expression patterns of these genes during different developmental stages, in various tissues of male and female adults, as well as in response to extreme temperatures and UV-A stress were studied via real-time quantitative polymerase chain reaction. The results showed that the expression levels of all five SfsHsp genes differed among the developmental stages as well as among the different tissues of male and female adults. The expression levels of most SfsHsp genes under extreme temperatures and UV-A-induced stress were significantly upregulated in both male and female adults. In contrast, those of SfsHsp20.1 and SfsHsp19.3 were significantly downregulated under cold stress in male adults. Therefore, the different SfsHsp genes of S. frugiperda play unique regulatory roles during development as well as in response to various environmental stressors.     

Intermediates in the Guanine Nucleotide Exchange Reaction of Rab8 Protein Catalyzed by Guanine Nucleotide Exchange Factors Rabin8 and GRAB

Small G-proteins of the Ras superfamily control the temporal and spatial coordination of intracellular signaling networks by acting as molecular on/off switches. Guanine nucleotide exchange factors (GEFs) regulate the activation of these G-proteins through catalytic replacement of GDP by GTP. During nucleotide exchange, three distinct substrate·enzyme complexes occur: a ternary complex with GDP at the start of the reaction (G-protein·GEF·GDP), an intermediary nucleotide-free binary complex (G-protein·GEF), and a ternary GTP complex after productive G-protein activation (G-protein·GEF·GTP). Here, we show structural snapshots of the full nucleotide exchange reaction sequence together with the G-protein substrates and products using Rabin8/GRAB (GEF) and Rab8 (G-protein) as a model system. Together with a thorough enzymatic characterization, our data provide a detailed view into the mechanism of Rabin8/GRAB-mediated nucleotide exchange.     

海藻中有机碘的研究Ⅰ.海藻中有机碘含量测定

采用国际上目前通用的差减法来计算海藻中的有机碘,即首先测定海藻中的总碘和无机碘,其差减值为有机碘.碘的测定采用了碘离子选择电极法和中子活化法作为对照。在此基础上,还测定了新鲜海带中碘的含量、分布以及有机碘和无机碘的比例。研究结果表明,海带中碘的平均含量占鲜重的0.133％,其中88％的碘是以碘离子的形式存在,有机碘只占总碘的12％,同时海带不同部位碘的含量不同,叶部外缘含碘较多,是叶中部的2倍左右,尤其叶尖部的含量达到鲜重的0.183％。而有机碘的含量分布规律则不同,有机碘的含量在靠近根部的位置较高,为鲜重的13.9％。这种分布特点可能与海带的生命活动规律有关。     

Identification of Small Molecule Inhibitors of Jumonji AT-rich Interactive Domain 1B (JARID1B) Histone Demethylase by a Sensitive High Throughput Screen

JARID1B (also known as KDM5B or PLU1) is a member of the JARID1 family of histone lysine demethylases responsible for the demethylation of trimethylated lysine 27 in histone H3 (H3K4me3), a mark for actively transcribed genes. JARID1B is overexpressed in several cancers, including breast cancer, prostate cancer, and lung cancer. In addition, JARID1B is required for mammary tumor formation in syngeneic or xenograft mouse models. JARID1B-expressing melanoma cells are associated with increased self-renewal character. Therefore, JARID1B represents an attractive target for cancer therapy. Here we characterized JARID1B using a homogeneous luminescence-based demethylase assay. We then conducted a high throughput screen of over 15,000 small molecules to identify inhibitors of JARID1B. From this screen, we identified several known JmjC histone demethylase inhibitors, including 2,4-pyridinedicarboxylic acid and catechols. More importantly, we identified several novel inhibitors, including 2-4(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one (PBIT), which inhibits JARID1B with an IC₅₀ of about 3 μm in vitro. Consistent with this, PBIT treatment inhibited removal of H3K4me3 by JARID1B in cells. Furthermore, this compound inhibited proliferation of cells expressing higher levels of JARID1B. These results suggest that this novel small molecule inhibitor is a lead compound that can be further optimized for cancer therapy.