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Activation of bacterial porin gene expression by a chimeric signal transducer in response to aspartate 总被引：13，自引：0，他引：13
R Utsumi R E Brissette A Rampersaud S A Forst K Oosawa M Inouye 《Science (New York, N.Y.)》1989,245(4923):1246-1249
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采用扫描电镜观察了蝶蛹金小蜂(Pteromalus puparum) L.触角表面的超微形态。观察结果表明,在触角基、柄节、梗节和鞭节上共存在着7种感觉器,分别为厚壁化学感器,薄壁化学感器,板状感器,短曲触觉毛,纤直触觉毛,锥形乳头状感器和刺形感器。对触角感觉器的形态、分布进行了描述,并对两性间的差别进行了讨论。 相似文献
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Sugar and signal-transducer binding sites of the Escherichia coli galactose chemoreceptor protein 总被引：11，自引：0，他引：11
D-galactose-binding (or chemoreceptor) protein of Escherichia coli serves as an initial component for both chemotaxis towards galactose and glucose and high-affinity active transport of the two sugars. Well-refined x-ray structures of the liganded forms of the wild-type and a mutant protein isolated from a strain defective in chemotaxis but fully competent in transport have provided a molecular view of the sugar-binding site and of a site for interacting with the Trg transmembrane signal transducer. The geometry of the sugar-binding site, located in the cleft between the two lobes of the bilobate protein, is novel in that it is designed for tight binding and sequestering of either the alpha or beta anomer of the D-stereoisomer of the 4-epimers galactose and glucose. Binding specificity and affinity are conferred primarily by polar planar side-chain residues that form intricate networks of cooperative and bidentate hydrogen bonds with the sugar substrates, and secondarily by aromatic residues that sandwich the pyranose ring. Each of the pairs of anomeric hydroxyls and epimeric hydroxyls is recognized by a distinct Asp residue. The site for interaction with the transducer is about 18 A from the sugar-binding site. Mutation of Gly74 to Asp at this site, concomitant with considerable changes in the local ordered water structures, contributes to the lack of productive interaction with the transmembrane signal transducer. 相似文献
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趋化作用在根瘤菌与宿主建立共生关系的起始阶段起着至关重要的作用。TlpA1是茎瘤固氮根瘤菌ORS571重要的跨膜趋化受体，但其感应机理尚未清楚。考察茎瘤固氮根瘤菌ORS571跨膜趋化受体TlpA1对趋化物的感应机理及生物学功能。通过平末端连接的方法构建N端表达菌株进行原核表达蛋白及纯化，利用等温滴定量热法（isothermal titration calorimetry）检测蛋白与趋化物的相互作用，测定野生型与突变株的生物膜及絮凝等表型。结果显示，跨膜趋化受体TlpA1通过胞外部分第29～183位氨基酸与琥珀酸结合。固氮条件下，突变株ΔTlpA1生物膜形成量相较于野生型下降约38%。絮凝量与野生型无显著性差异。跨膜趋化受体TlpA1通过感应琥珀酸调控茎瘤固氮根瘤菌ORS571生物膜的形成，对细胞絮凝无调控作用。 相似文献
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趋化作用在根瘤菌与宿主建立共生关系的起始阶段起着至关重要的作用。TlpA1是茎瘤固氮根瘤菌ORS571重要的跨膜趋化受体，但其感应机理尚未清楚。考察茎瘤固氮根瘤菌ORS571跨膜趋化受体TlpA1对趋化物的感应机理及生物学功能。通过平末端连接的方法构建N端表达菌株进行原核表达蛋白及纯化，利用等温滴定量热法（isothermal titration calorimetry）检测蛋白与趋化物的相互作用，测定野生型与突变株的生物膜及絮凝等表型。结果显示，跨膜趋化受体TlpA1通过胞外部分第29～183位氨基酸与琥珀酸结合。固氮条件下，突变株ΔTlpA1生物膜形成量相较于野生型下降约38%。絮凝量与野生型无显著性差异。跨膜趋化受体TlpA1通过感应琥珀酸调控茎瘤固氮根瘤菌ORS571生物膜的形成，对细胞絮凝无调控作用。 相似文献
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The responses of a taste nerve in rats to sodium chloride were integrated over successive 10-millisecond intervals and averaged. The time course of the mean responses consisted of a 30-millisecond latency, a rapid rise to a maximum, and a slower decline to a sustained level. The chemoreceptor theories of Beidler and Paton failed to predict the relation between phasic response and time or concentration. 相似文献
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GUNTER G 《Science (New York, N.Y.)》1961,133(3449):327-328
A chemoreceptor neuron of the adult blowfly contains several different sites for activation by sugars. It appears that the number or affinity of the sites for fructose and perhaps those for glucose may be depressed by rearing the larvae in the presence of the sugar in question. 相似文献
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R Schafer 《Science (New York, N.Y.)》1973,180(83):315-317
Acetylcholine is transported along insect chemoreceptor axons at a rate of 12 to 13 centimeters per day after peripheral uptake of choline. Colchicine, vinblastine sulfate, and cytochalasin B all block transport, but transport continues in axons separated surgically from the cell body. These data from an insect are in accord with many studies on vertebrates which have implicated intracellular microtubules in the transport mechanism. The peripheral uptake of choline and its acetylation and transport to nerve terminals in the brain are consistent withthe suggestion that acetylcholine is an antennal sensory transmitter in insects. 相似文献
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Animals alter their behavioral patterns in an experience-dependent manner. Olfactory imprinting is a process in which the exposure of animals to olfactory cues during specific and restricted time windows leaves a permanent memory ("olfactory imprint") that shapes the animal's behavior upon encountering the olfactory cues at later times. We found that Caenorhabditis elegans displays olfactory imprinting behavior that is mediated by a single pair of interneurons. To function in olfactory imprinting, this interneuron pair must express a G protein-coupled chemoreceptor family member encoded by the sra-11 gene. Our study provides insights into the cellular and molecular basis of olfactory imprinting and reveals a function for a chemosensory receptor family member in interneurons. 相似文献
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[目的]了解狼蛛捕食行为的影响因子。[方法]以拟水狼蛛为研究对象,采用L_9(3~4)正交试验设计,探讨了狼蛛嗅觉感受器对捕食行为(寻觅、选择与定位猎物)的影响,并对不同反应观察时长提出试验设计方案。试验全过程在25℃恒温环境完成,采用四臂嗅觉仪测定。[结果]间距对狼蛛定位果蝇灵敏度的影响最大,其次是果蝇组织液浓度和狼蛛反应时长观察。经正交试验统计检验,得出狼蛛定位猎物的最佳优化组合为果蝇体液浓度80%、距离为6 cm、狼蛛反应时长300 s,此时狼蛛嗅觉感受器灵敏度最高。[结论]试验结果为制定保护和利用蜘蛛防治害虫的措施提供了理论依据。 相似文献
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Identification of HTLV-III/LAV sor gene product and detection of antibodies in human sera 总被引：24，自引：0，他引：24
N C Kan G Franchini F Wong-Staal G C DuBois W G Robey J A Lautenberger T S Papas 《Science (New York, N.Y.)》1986,231(4745):1553-1555
The nucleotide sequence of the genome of HTLV-III, the infectious agent etiologically associated with the acquired immune deficiency syndrome, predicts a small open reading frame, termed sor, located between the pol and env genes. A DNA segment containing 82 percent of the sor region was inserted into a prokaryotic expression vector, pJL6, to determine whether sor encodes a viral protein and to gain some insight into its possible function. The bacterially synthesized sor protein reacted with sera from individuals infected with HTLV-III, indicating that sor is expressed as a protein product or products that are immunogenic in vivo. Antibodies to the purified, bacterially synthesized sor protein were found to react specifically with the same protein and also with a protein of molecular weight 23,000 (23K) in HTLV-III-infected H9 cell extracts. The 23K protein comigrated with a protein immunoprecipitated by the serum of a hemophiliac patient with antibodies to HTLV-III, suggesting that this protein is probably the sor gene product. 相似文献
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以大麦虫幼虫脱脂粉为原料,根据溶解性的不同,从中分离出水溶蛋白、酸溶蛋白、醇溶蛋白及碱溶蛋白,并对各蛋白组分进行体外抗氧化性研究。结果表明:大麦虫幼虫脱脂粉中最主要的蛋白组分为水溶蛋白,占脱脂虫粉的30.24%;其次为碱溶蛋白19.45%;酸溶蛋白和醇溶蛋白分别占9.52%和4.43%。大麦虫各蛋白组分均有体外抗氧化作用,随着浓度的增大,各蛋白液的总还原能力、对羟基自由基和超氧阴离子自由基的清除能力也随之增强。水溶蛋白具有最强的还原力和清除超氧阴离子能力,酸溶蛋白清除羟基自由基能力最强。 相似文献
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钠、钾离子对Bt蛋白在蒙脱石和凹凸棒土表面吸附与解吸的影响 总被引：1，自引：1，他引：0
采用静态吸附法研究了钠、钾离子对苏云金杆菌杀虫蛋白在蒙脱石和凹凸棒土表面吸附与解吸特性的影响。结果表明,添加钠、钾离子(0~2 mmol.L-1)均可提高Bt蛋白在两种矿物上的平衡吸附量,但等温吸附曲线的Langmuir方程拟合基本没受影响。添加钠离子或钾离子均能引起矿物粒子Zeta负电位升高,提示钠、钾离子通过减小矿物粒子与Bt蛋白之间斥力的方式促进了Bt蛋白吸附。在蒙脱石吸附Bt蛋白过程中添加钠、钾离子可使Bt蛋白的水解吸率升高,但解吸后的残留量变化不大;在凹凸棒土吸附Bt蛋白过程中添加钠、钾离子可使Bt蛋白的水解吸率减小,且解吸后的残留量增加。 相似文献
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P65蛋白是猪肺炎支原体的主要免疫优势蛋白,与其他支原体无交叉反应,常作为猪肺炎支原体检测的靶蛋白。本实验应用原核表达的重组 P65蛋白免疫小鼠,用 Mhp全菌蛋白和P65蛋白筛选,制备了1株特异性单克隆抗体3G12。鉴定结果表明,该株单克隆抗体可与 P65蛋白和 Mhp全菌蛋白反应,采用间接 ELISA法测得3G12细胞培养上清与P65蛋白反应抗体的效价为1∶12800,与全菌蛋白反应抗体的效价为1∶3200;3G12腹水与P65蛋白反应的抗体效价为1∶4000000以上,与168全菌蛋白反应的抗体效价为1∶20000以上,细胞经长期体外培养和冻存后复苏能稳定分泌抗体。本研究成功获得到1株针对 P65和Mhp全菌的单克隆抗体,为猪肺炎支原体致病机制和检测方法的进一步研究提供了基础。 相似文献
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The observation of the regulation of fast protein dynamics in a cellular context requires the development of reliable technologies. Here, a signal regulation cascade reliant on the stimulus-dependent acceleration of the bidirectional flow of mitogen-activated protein kinase (extracellular signal-regulated kinase) across the nuclear envelope was visualized by reversible protein highlighting. Light-induced conversion between the bright and dark states of a monomeric fluorescent protein engineered from a novel coral protein was employed. Because of its photochromic properties, the protein could be highlighted, erased, and highlighted again in a nondestructive manner, allowing direct observation of regulated fast nucleocytoplasmic shuttling of key signaling molecules. 相似文献
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A role for a 70-kilodalton heat shock protein in lysosomal degradation of intracellular proteins 总被引：44，自引：0，他引：44
A 73-kilodalton (kD) intracellular protein was found to bind to peptide regions that target intracellular proteins for lysosomal degradation in response to serum withdrawal. This protein cross-reacted with a monoclonal antibody raised to a member of the 70-kD heat shock protein (hsp70) family, and sequences of two internal peptides of the 73-kD protein confirm that it is a member of this family. In response to serum withdrawal, the intracellular concentration of the 73-kD protein increased severalfold. In the presence of adenosine 5'-triphosphate (ATP) and MgCl2, the 73-kD protein enhanced protein degradation in two different cell-free assays for lysosomal proteolysis. 相似文献