触形大疣蛛毒素多肽的分离和鉴定

蜘蛛是种类最多的有毒动物,其毒液主要成分是富含二硫键的毒素多肽。蜘蛛毒素多肽主要功能是作用于昆虫神经系统的离子通道或受体。触形大疣蛛隶属于蜘蛛目,原蛛下目,异纺蛛科。通过反相高效液相色谱分离触形大疣蛛粗毒,再通过MALDI-TOF-TOF质谱对各个洗脱峰进行分子量测定。实验结果显示,从触形大疣蛛粗毒中一共鉴定到108种的毒素多肽,其分子量在2 000~7 500 Da均有分布,主要分子量范围分布在2 000~4 500 Da(占63.9%),还有一部分分布在4 500~6 000 Da,而在6 000~7 500 Da范围内分布很少。其分子量的分布特征与已报道的原蛛下目蜘蛛均不同,反映了这种蜘蛛毒液成分具有独特的多样性。     

Peptide neurotoxins from fish-hunting cone snails

To paralyze their more agile prey, the venomous fish-hunting cone snails (Conus) have developed a potent biochemical strategy. They produce several classes of toxic peptides (conotoxins) that attack a series of successive physiological targets in the neuromuscular system of the fish. The peptides include presynaptic omega-conotoxins that prevent the voltage-activated entry of calcium into the nerve terminal and release of acetylcholine, postsynaptic alpha-conotoxins that inhibit the acetylcholine receptor, and muscle sodium channel inhibitors, the mu-conotoxins, which directly abolish muscle action potentials. These distinct peptide toxins share several common features: they are relatively small (13 to 29 amino acids), are highly cross-linked by disulfide bonds, and strongly basic. The fact that they inhibit sequential steps in neuromuscular transmission suggests that their action is synergistic rather than additive. Five new omega-conotoxins that block presynaptic calcium channels are described. They vary in their activity against different vertebrate classes, and also in their actions against different synapses from the same animal. There are susceptible forms of the target molecule in peripheral synapses of fish and amphibians, but those of mice are resistant. However, the mammalian central nervous system is clearly affected, and these toxins are thus of potential significance for investigating the presynaptic calcium channels.     

α-芋螺毒素与烟碱型乙酰胆碱受体作用的药理学

芋螺毒素(CTX)来源于芋螺毒管分泌的毒液,是一类分子质量小、结构新颖、作用靶点广泛且特异性高的活性多肽,具有开发成为药物或药物先导化合物的价值。芋螺毒素按其作用靶点不同等特点可以分为多个家族,其中α-芋螺毒素家族(α-CTXs)的半胱氨酸模式为:CC-C-C。根据α-CTXs半胱氨酸残基间的氨基酸数目进一步分为不同的亚家族。α-CTXs是肌肉或神经型烟碱乙酰胆碱受体的选择性拮抗剂,具有重要临床意义的乙酰胆碱受体(nAChRs)与神经痛、帕金森病、痴呆、学习记忆障碍以及小细胞肺癌等多种疾病的发病、诊断和治疗密切相关。笔者详述了α-芋螺毒素与烟碱型乙酰胆碱受体的结构、分类及其相互间的作用关系,旨在为该类药物的开发利用提供参考依据。     

Structural analysis of the mechanism of adenovirus binding to its human cellular receptor, CAR

Binding of virus particles to specific host cell surface receptors is known to be an obligatory step in infection even though the molecular basis for these interactions is not well characterized. The crystal structure of the adenovirus fiber knob domain in complex with domain I of its human cellular receptor, coxsackie and adenovirus receptor (CAR), is presented here. Surface-exposed loops on knob contact one face of CAR, forming a high-affinity complex. Topology mismatches between interacting surfaces create interfacial solvent-filled cavities and channels that may be targets for antiviral drug therapy. The structure identifies key determinants of binding specificity, which may suggest ways to modify the tropism of adenovirus-based gene therapy vectors.     

柿子单宁对几种蛇毒中主要酶的抑制作用及其机理初探

 【目的】分析柿子单宁（persimmon tannin,PT）对江浙蝮蛇、尖吻蝮蛇、眼镜蛇毒中主要酶活力的抑制作用,初步研究两者相互作用的机理。【方法】将蛇毒与PT以不同比例混合后在37℃下温育1 h,离心分离,测定上清液中主要酶活力变化,并采用SDS-聚丙烯酰胺凝胶电泳对粗毒和作用后所得沉淀及上清液进行分析。【结果】当蛇毒与PT质量比达到1﹕1时,粗毒中蛋白质水解酶、磷脂酶A2、L-氨基酸氧化酶、精氨酸酯酶、乙酰胆碱酯酶、类凝血酶活力被完全抑制,且酶活力的下降与PT含量呈剂量增加效应;SDS-聚丙烯酰胺电泳表明,PT与蛇毒蛋白具有很强的非特异性结合能力。但对不同结构蛋白质结合能力和选择性也明显不同。【结论】柿子单宁在体外条件下对蛇毒中几种酶的活力具有明显的抑制作用,PT与蛋白结合是导致酶失活的重要原因。     

松树蜂毒素腺解剖结构和毒素成分

以在黑龙江、内蒙古松树蜂(Sirex noctilio)发生区采集的松树蜂为研究对象,解剖松树蜂雌成虫腹部找到毒素腺和毒素囊的位置并在显微镜下观察其结构特点;用赛默飞气相色谱质谱联用仪,设定50℃开始升温,在5℃·min-1升到200℃条件下分析毒素成分。结果表明:毒素腺和毒素囊位于松树蜂的产卵器基部,毒素囊为绿豆粒大小半透明晶状组织,其结构特点有利于松树蜂储存尽可能多的毒素。毒素含有生物碱、糖及糖苷、脂肪酸和蛋白质等物质,其中脂肪酸类物质占主要比例,包括棕榈酸、十六碳烯酸、硬脂酸、十八烷酸等酸,毒素成分中的蛋白质可能是对寄主树木造成伤害的活性物质。     

Stress and the toxicity of venoms

Animals injected with venom of the scorpion Centruroides sculpturatus Ewing or venom of the rattlesnake Crotalus atrox Baird and Girard were subjected to high-and low-temperature stress. Unconditioned animals transferred to a modified temperature were less refractory to the venoms than those conditioned for 48 hours, but all animals stressed were less refractory than unstressed animals. Animals receiving a series of small doses of epinephrine were similarly affected. This apparent change in toxicity of the venoms seems to be due to the physiological effects of stress rather than to the temperature per se.     

Fertilization events induced by neurotransmitters after injection of mRNA in Xenopus eggs

Fertilization initiates in the egg a dramatic increase in intracellular calcium that opens ion channels and causes exocytosis. To explore the possibility that these events might involve a receptor-mediated pathway, receptors for serotonin or acetylcholine (M1 muscarinic) were expressed in the Xenopus egg; serotonin or acetylcholine then could initiate a series of responses similar to those normally initiated by sperm. Thus, there may be an endogenous receptor in the egg membrane that is activated by sperm, and the serotonin or M1 muscarinic receptor may replace the sperm receptor in this pathway.     

N-Formylmethionyl peptide receptors on equine leukocytes initiate secretion but not chemotaxis

The chemotaxis of leukocytes appears to be initiated by the binding of chemotactic factors to the surface of these cells. N-Formylated peptides induce chemotaxis and lysosomal enzyme secretion of leukocytes; because these peptides are available in a purified radiolabeled form, they have been useful in the characterization of receptors for chemotactic factors. Equine polymorphonuclear leukocytes secrete lysosomal enzymes but do not exhibit chemotaxis in respone to the N-formylated peptides, even though they have a high-affinity cell surface receptor for these agents. The specificity of the equine receptor resembles the specificity of the receptor on chemotactically responsive leukocytes from other species. Equine polymorphonuclear leukocytes may thus be an excellent model for the study of the events that lead to a biological response following receptor occupancy.     

Mast cells can enhance resistance to snake and honeybee venoms

Snake or honeybee envenomation can cause substantial morbidity and mortality, and it has been proposed that the activation of mast cells by snake or insect venoms can contribute to these effects. We show, in contrast, that mast cells can significantly reduce snake-venom-induced pathology in mice, at least in part by releasing carboxypeptidase A and possibly other proteases, which can degrade venom components. Mast cells also significantly reduced the morbidity and mortality induced by honeybee venom. These findings identify a new biological function for mast cells in enhancing resistance to the morbidity and mortality induced by animal venoms.     

Transient expression shows ligand gating and allosteric potentiation of GABAA receptor subunits

Human gamma-aminobutyric acid A (GABAA) receptor subunits were expressed transiently in cultured mammalian cells. This expression system allows the simultaneous characterization of ligand-gated ion channels by electrophysiology and by pharmacology. Thus, coexpression of the alpha and beta subunits of the GABAA receptor generated GABA-gated chloride channels and binding sites for GABAA receptor ligands. Channels consisting of only alpha or beta subunits could also be detected. These homomeric channels formed with reduced efficiencies compared to the heteromeric receptors. Both of these homomeric GABA-responsive channels were potentiated by barbiturate, indicating that sites for both ligand-gating and allosteric potentiation are present on receptors assembled from either subunit.     

Blockade of "NMDA" receptors disrupts experience-dependent plasticity of kitten striate cortex

Intracortical infusion of the "N-methyl-D-aspartate" (NMDA) receptor blocker D,L-2-amino-5-phosphonovaleric acid (APV) renders kitten striate cortex resistant to the effects of monocular deprivation. In addition, 1 week of continuous APV treatment (50 nanomoles per hour) produces a striking loss of orientation selectivity in area 17. These data support the hypothesis that crucial variables for the expression of activity-dependent synaptic modifications are a critical level of postsynaptic activation and calcium entry through ion channels linked to NMDA receptors.     

Impaired thermosensation in mice lacking TRPV3, a heat and camphor sensor in the skin

Environmental temperature is thought to be directly sensed by neurons through their projections in the skin. A subset of the mammalian transient receptor potential (TRP) family of ion channels has been implicated in this process. These "thermoTRPs" are activated at distinct temperature thresholds and are typically expressed in sensory neurons. TRPV3 is activated by heat (>33 degrees C) and, unlike most thermoTRPs, is expressed in mouse keratinocytes. We found that TRPV3 null mice have strong deficits in responses to innocuous and noxious heat but not in other sensory modalities; hence, TRPV3 has a specific role in thermosensation. The natural compound camphor, which modulates sensations of warmth in humans, proved to be a specific activator of TRPV3. Camphor activated cultured primary keratinocytes but not sensory neurons, and this activity was abolished in TRPV3 null mice. Therefore, heat-activated receptors in keratinocytes are important for mammalian thermosensation.     

Venom Collection from Honey Bees

A device that provides an electric shock makes it possible to collect pure venom from several thousand honey bees (Apis mellifera). The collection apparatus fits underneath the brood chamber of a colony of bees and may be moved from hive to hive. Each colony is "milked" for 5 minutes. An average of 20 hives must be "milked" to obtain 1 gram of venom. Under optimum conditions this quantity of venom is produced by 10,000 worker bees.     

Nicotinic Acetylcholine Receptor Gene Family of the Pea Aphid,Acyrthosiphon pisum

The nicotinic acetylcholine receptors （nAchRs） are cholinergic receptors that form ligand-gated ion channels by ifve subunits in insect and vertebrate nervous systems. The insect nAChR is the molecular target of a class of insecticides, neonicotinoids. Here, we identiifed and cloned 11 candidate nAChR subunit genes in Acyrthosiphon pisum using genome-based bioinformatics combined modern molecular techniques. Most A. pisum nAChRs including α1, α2, α3, α4, α6, α8, and β1 show highly sequence identities with the counterparts of other insects examined. Expression proifles analysis showed that all subunit genes were expressed in adult head. At least two subunits have alternative splicing that obviously increase A. pisum nicotinic receptor diversity. This study will be invaluable for exploring the molecular mechanisms of neonicotinoid-like insecticides in sucking pests, and for ultimately establishing the screening platform of novel insecticides.     

The coupling of neurotransmitter receptors to ion channels in the brain

Recent studies on the action of neurotransmitters on hippocampal pyramidal cells indicate that different neurotransmitter receptors that use either the same or different coupling mechanisms converge onto the same ion channel. Conversely, virtually all of the neurotransmitters act on at least two distinct receptor subtypes coupled to different ion channels on the same cell. The existence of both convergence and divergence in the action of neurotransmitters results in a remarkable diversity in neuronal signaling.     

Benzodiazepine receptor-mediated chemotaxis of human monocytes

Benzodiazepines, which are widely prescribed for their antianxiety effects, are shown to be potent stimulators of human monocyte chemotaxis. The chemotactic effects of benzodiazepine receptor agonists were blocked by the peripheral benzodiazepine receptor antagonist PK-11195, suggesting that these effects are mediated by the peripheral-type benzodiazepine receptor. Diazepam was also active in inducing chemotaxis. Binding studies on purified monocytes revealed high-affinity peripheral benzodiazepine receptors, and the displacement potencies of various benzodiazepines correlated with their relative potencies in mediating chemotaxis. The demonstration of functional benzodiazepine receptors on human monocytes, together with recent evidence of receptor-mediated monocyte chemotaxis by other psychoactive peptides (such as opiate peptides), suggests a biochemical substrate for psychosomatic communication.     

Comparative toxinology of Loxosceles reclusa and Corynebacterium pseudotuberculosis

In contrast to other kinds of phospholipases, phospholipases D that are toxic for humans and animals are not commonly encountered as constituents of venoms or as products of pathogenic microorganisms. Toxic phospholipases D are present, however, in the venom of the brown recluse spider (Loxosceles reclusa) and in supernatants or filtrates of cultures of Corynebacterium pseudotuberculosis. Although the two enzyme toxins are derived from phylogenetically disparate entities, they are similar in molecular weight, charge, substrate specificity, and in several biological activities. They are immunologically distinguishable.     

Chromatographic comparison of scorpion venoms

The venom of seven species of scorpions Was subjected to two-dimensional chromratographic analysis. Six major components were defined and tentatively correlated with the physiological activity of the venoms.     

Synthetic amphiphilic peptide models for protein ion channels

Ion channel proteins are important for the conduction of ions across biological membranes. Recent analyses of their sequences have suggested that they are composed of bundles of alpha-helices that associate to form ion-conducting channels. To gain insight into the mechanisms by which alpha-helices can aggregate and conduct ions, three model peptides containing only leucine and serine residues were synthesized and characterized. A 21-residue peptide, H2N-(Leu-Ser-Ser-Leu-Leu-Ser-Leu)3-CONH2, which was designed to be a membrane-spanning amphiphilic alpha-helix, formed well-defined ion channels with ion permeability and lifetime characteristics resembling the acetylcholine receptor. In contrast, a 14-residue version of this peptide, which was too short to span the phospolipid bilayer as an alpha-helix, failed to form discrete, stable channels. A third peptide, H2N-(Leu-Ser-Leu-Leu-Leu-Ser-Leu)3-CONH2, in which one serine per heptad repeat was replaced by leucine, produced proton-selective channels. Computer graphics and energy minimization were used to create molecular models that were consistent with the observed properties of the channels.