Simple Synthesis of Climacostol,a Defensive Secretion by the Ciliate Climacostomum virens

Climacostol {1,3-dihydroxy-5-[(Z)-2'-nonenyl]benzene,1}, a defensive secretion by the protozoan ciliate Climacostomum virens against predators, was synthesized in a 43% overall yield in three steps by starting from methyl 1,3-bis(tert-butyldimethylsilyloxy) phenylacetate (3).     

About lipids and toxins

Many mono or multicellular organisms secrete soluble proteins, referred to as protein toxins, which alter the behavior of foreign, or target cells, possibly leading to their death. These toxins affect either the cell membrane by forming pores or modifying lipids, or some intracellular target. To reach this target, they must cross one of the cellular membranes, generally that of an intracellular organelle. As described in this minireview, lipids play crucial roles in the intoxication process of most if not all toxins, by allowing/promoting binding, endocytosis, trafficking and/or translocation into the cytoplasm.     

Does uptake of Alexandrium fundyense cysts contribute to the levels of PSP toxin found in the sea scallop, Placopecten magellanicus?

Atlantic sea scallops, Placopecten magellanicus, in most areas of the Bay of Fundy, New Brunswick, Canada, have year-round concentrations of paralytic shellfish posioning (PSP) toxins greater than the regulatory concentration of 80 μg STX eq. 100 g⁻¹ wet weight. Scallops (mean shell height of 10.7 cm, age 3–5 years) were collected by SCUBA and individually tagged near Parker Island, Bay of Fundy. Half were hung 2 m below the low tide water level and the remainder were placed on the bottom (11 m depth at low tide) under the scallops held at 2 m. Scallop, water and sediment samples were collected monthly for determination of concentrations of PSP toxins and Alexandrium fundyense.In October, 1993, mean concentrations of PSP toxins in digestive gland, and mantle were 3205 and 1018 μg STX eq. 100 g⁻¹ wet weight, respectively. Eight months later (June 1994), PSP concentrations in digestive glands from the surface and bottom had declined to 504 and 682 μg STX eq. 100 g⁻¹ wet weight, respectively, whereas those in the mantle had declined to 802 and 681 μg STX eq. 100 g⁻¹ wet weight. During July 1994, A. fundyense concentrations observed at Parker Island and offshore were 320 cells l⁻¹ and 14,200 cells l⁻¹, respectively. Subsequently, toxin concentrations in surface and bottom scallop digestive glands increased to 12,720 and 11,408 μg STX eq. 100 g⁻¹ wet weight, whereas concentrations in mantles increased to 2126 and 1748 μg STX eq. 100 g⁻¹ wet weight, respectively. Concentrations of PSP toxins in these tissues in October 1994 were similar to those measured in October 1993. Concentrations of PSP toxin were less than the regulatory concentration in the gonads and non-detectable in adductor muscles of all scallops sampled.There were no statistically significant differences in profiles for uptake and depuration of PSP toxins in scallops held at the surface compared to those from bottom, suggesting that A. fundyense cysts at the concentrations found in the sediment (45 cysts cm⁻³) did not contribute significantly to the year-round presence of PSP toxins within scallop tissues. The year-round occurrence of PSP toxin is probably due to accumulation during summer blooms followed by a very slow rate of depuration.     

Molecular properties and metabolic effect on blood cells produced by a new toxin of Enterobacter cloacae

A new toxin of Enterobacter cloacae able to lyse erythrocytes and leukocytes was found. Purification of the toxin was performed by salt precipitation, gel filtration, ion exchange and HPLC in C₈ column. SDS-PAGE electrophoresis showed more than one bank corresponding to the leukotoxin able to form polymers and aggregate like some pore-forming cytotoxins (RTX). In culture supernatant the toxin showed 1 HU/ml (hemolytic unit) and 1.5 LU/ml (leukotoxic unit); after purification it reached 15 HU/ml and 20 LU/ml. The ratio between HU and percentage red cells affected the lytic capacity. E. cloacae toxin stimulated the oxidative metabolism of neutrophils, but over 50 μg toxin/ml the stimulus ceased as it was shown by NBT assay due to cell death. Chemiluminescence evidenced an increase in superoxide anion generation, but an excess of toxin interfered with this stimulus, as was previously observed in HlyA Escherichia coli toxin. Cross-reaction was found by immunoblotting with this HlyA. E. cloacae toxin presented higher amounts of proline, valine, aspartic and glutamic acids than HlyA. E. cloacae toxin was similar to HlyA in the prescence of a glycine-rich DNA sequence and in the observed effect of calcium on toxin activity. E. cloacae toxin did not cross-react by immunoblotting with hemolysin HmpA of Proteus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Functional lysophosphatidic acid receptors expressed in Oryzias latipes

Lysophosphatidic acid (LPA) signaling is known to play biological and pathophysiological roles in many types of animals. Medaka (Oryzias latipes) is an experimental fish that can be easily maintained, propagated, and analyzed, and whose genome has been completely sequenced. However, there is limited information available regarding medaka LPA receptors. Here, using information from the medaka genome database, we examine the genomic structures, expression, and functions of six LPA receptor genes, Lpar1–Lpar6. Our analyses reveal that the genomic structures of Lpar1 and Lpar4 are different from those deduced from the database. Functional analyses using a heterologous expression system demonstrate that all medaka LPA receptors except for LPA_5b respond to LPA treatment with cytoskeletal changes. These findings provide useful information on the structure and function of medaka LPA receptor genes, and identify medaka as a useful experimental model for exploration of the biological significance of LPA signaling.     

Expression in yeast of a cDNA copy of the K2 killer toxin gene

Summary A cDNA copy of the M2 dsRNA encoding the K2 killer toxin ofSaccharomyces cerevisiae was expressed in yeast using the yeastADH1 promoter. This construct produced K2-specific killing and immunity functions. Efficient K2-specific killing was dependent on the action of the KEX2 endopeptidase and the KEX1 carboxypeptidase, while K2-specific immunity was independent of these proteases. Comparison of the K2 toxin sequence with that of the K1 toxin sequence shows that although they share a common processing pathway and are both encoded by cytoplasmic dsRNAs of similar basic structure, the two toxins are very different at the primary sequence level. Site-specific mutagenesis of the cDNA gene establishes that one of the two potential KEX2 cleavage sites is critical for toxin action but not for immunity. Immunity was reduced by an insertion of two amino acids in the hydrophobic amino-terminal region which left toxin activity intact, indicating an independence of toxin action and immunity.     

胸膜肺炎放线杆菌RTX毒素与宿主的相互作用

摘要：胸膜肺炎放线杆菌引起猪传染性胸膜肺炎,给养猪业造成严重的经济损失。RTX毒素是胸膜肺炎放线杆菌主要的毒力因子,在该病原的感染与免疫中发挥“双刃剑”的作用。本文综述了近十多年来国内外在胸膜肺炎放线杆菌RTX毒素的研究进展,提出了毒素与宿主互作研究的必要性和技术可行性,认为毒素与宿主相互作用研究将诠释此病原的分子致病机理。     

水稻基腐病细菌毒素的遗传特性和产毒相关的分子标记

[目的]水稻基腐病(Erwinia chrysanthemi pv.zeae)是水稻上重要的细菌病害之一,本论文对该病菌的毒素遗传特性和产毒相关的分子标记进行了研究.[方法]通过化学诱变方法,筛选基腐细菌去质粒的突变体Ech7-mu1;应用RAPD技术,筛选产毒素相关的分子标记.[结果]毒素活性测定结果表明,野生菌Ech7和去质粒菌株Ech7-mu1都能产生毒素.从260条随机引物中,筛选出引物K10,该引物能从不产生毒素的突变株Ech7-4中扩增出大小为2139bp的DNA特异片段,但不能扩增野生菌Ech7,将该片段克隆,测序分析,设计特异引物,在突变体Ech7-4中获得了与毒素产生相关的SCAR分子标记(标记符合率为100%).该基因片段有5个ORFs,其中2个ORFs分别编码NADH-黄素还原酶和N-乙酰转移酶,另外2个不完整的ORFs编码的蛋白分别与Pseudomonas aerginosa(ZP00136947)和Yersinia Pestis(ZP01177873)的抗菌素代谢转运蛋白通透酶(DMT)具有66%和46%的同源率.[结论]水稻基腐细菌毒素的生物合成是由染色体基因编码,与质粒无关.不产生毒素的突变菌株基因突变的位点位于SCAR标记DNA的3'末端.     

转基因烟草生产霍乱毒素B亚单位的纯化

提取转基因烟草叶片总蛋白,用经溴化氰活化的Ｓｅｐｈａｒｏｓｅ ４Ｂ偶联有抗ＣＴ ＩｇＧ色谱柱,得到了表达产物ＣＴＢ蛋白质。经ＰＡＧＥ、Ｗｅｓｔｅｒｎ ｂｌｏｔ、琼脂糖免疫扩散和免疫电泳等方法鉴定表明该蛋白与天然ＣＴＢ相同。     

Bt毒蛋白Cry1Ac在人造土壤中对赤子爱胜蚓毒理及生化影响

Bt毒素能通过转基因作物的花粉、根和残株进入土壤.为评估转基因作物对土壤动物的影响,本文模拟转基因棉的Bt毒素进入土壤的发生程度,用含不同浓度Bt毒蛋白Cry1Ac的人造土壤处理蚯蚓,测定蚯蚓存活率、重量变化及体内总蛋白含量和过氧化氢酶(CAT)、乙酰胆碱酯酶(AchE)、谷胱甘肽-S-转移酶(GST)和纤维素酶活性.结果表明,Bt毒蛋白对蚯蚓的生物量和生理水平影响均不明显,不存在急毒性和亚致死毒性影响,对蚯蚓比较安全.