多肽的表面展示与结构库

表面展示是一种新的基因操作技术,它使表达的多肽以融合蛋白形式展现在噬菌体或细胞表面,保持相对独立的空间结构和生物活性。该技术可用于研究多肽(蛋白质)的性质、相互识别和作用,并据此从巨大展示库中选择特定靶功能的多肽结构。常用丝状噬菌体、T₄噬菌体、λ噬菌体以及细胞构建表面展示系统。表面展示库包括重组噬菌体抗体库、随机短肽库、多肽构象库、cDNA展示库和基因突变体展示库。表面展示技术可用于人工抗体和疫苗的制备、抗原决定簇的定位、蛋白质相互作用位点的确定、特异调节分子的分离、细胞表面工程的研究、多肽药物的研制,以及生物分子实验定向进化等研究。     

Interaction of peptide antigens and class II major histocompatibility complex antigens

T lymphocytes require a foreign antigen to be presented on a cell surface in association with a self-transplantation antigen before they can recognize it effectively. This phenomenon is known as major histocompatibility complex (MHC) restriction. It is not clear how an incalculably large number of foreign proteins form unique complexes with a very limited number of MHC molecules. We studied the recognition properties of T cells specific for a peptide derived from bacteriophage lambda cI protein. Analogues of this peptide, as well as peptides derived from other unrelated antigens which can be presented in the context of the same MHC molecule, can competitively inhibit activation of these T cells by the cI peptide. Furthermore, these unrelated antigens can stimulate cI-specific T cells if certain specific amino-acid residues are replaced. Here we suggest a model in which all antigens give rise to peptides that can bind to the same site on the MHC molecule. T-cell recognition of this site (which is presumed to be polymorphic) with or without antigen bound can explain self-selection in the thymus and MHC restriction.     

A novel peptide,selected from phage display library of random peptides,can efficiently target into human breast cancer cell

To develop a targeting vector for breast cancer biotherapy, MDA-MB-231 cell, a human breast cancer cell line, was co-cultured with pC89 （9 aa） phage display library of random peptides. In multiple inde-pendent peptide-presenting phage screening trials, subtilisin was used as a protease to inactivate extra-cellular phages. The internalized phages were collected by cell lysising and amplified in E. coli XLI-Blue. Through five rounds of selection, the pepUde-presenting phages which could be internalized in MDA-MB-231 cells were isolated. A comparison was made between internalization capacities of peptide-presenting phages isolated from MDA-MB-231 cells and RGD-integrin binding phage by coculturing them with other human tumor cell lines and normal cells. The nucleoUde sequences of isolated peptide-presenting phages were then determined by DNA sequencing. To uncover whether phage coat protein or amino acid order was required for the character of the pepUde to MDA-MB-231 cells, three peptides were synthesized. They are CASPSGALRSC, ASPSGALRS and CGVIFDHSVPC （the shifted sequence of CASPSGALRSC）, and after coculturing them with different cell lines, their targeting capacities to MDA-MB-231 cells were detected. These data suggested that the internalization process was highly selective, and capable of capturing a specific peptide from parent peptide variants. Moreover, the targeting internalization event of pepUdes was an amino acid sequence dependent manner. The results demonstrated the feasibility of using phage display library of random peptides to develop new targeting system for intracellular delivery of macromolecules, and the peptide we obtained might be modified as a targeting vector for breast cancer gene therapy.     

利用噬菌体展示筛选结合水稻条叶枯病毒S蛋白的短肽

利用噬菌体展示技术在随机7肽库中筛选到结合水稻条叶枯病毒（rice stripe virus ,RSV）病害特异蛋白（stripe disease-specific protein,S蛋白）的6个短肽,并进行了序列测定,ELISA结果表明,6个短肽和S蛋白具有一定的亲和能力,筛选到的短肽对今后S蛋白功能分析、转基因抗RSV和水稻条叶枯病的诊断提供了条件。     

Expression of human hepatitis C virus core antigen in tobacco plants by tobacco mosaic virus-based vector system

Tobacco mosaic virus (TMV) has the potential to highly express foreign gene. A novel TMV-basedin trans expression system was constructed. A TMV mutant TSHc had its coat protein replaced with hepatitis C virus (HCV) core antigen gene. Anotherr TMV mutant TSBD was replicase-defective. Coinfection of the two mutants could cause systemic infection in tobacco plants byin trans complementation of their functions. TSHc could effectively replicate and assemble to viral particles, which were a little longer than that of wild-type TMV. HCV core antigen was expressed in whole tobacco plants. A similar expression level of HCV core antigen was detected on serial passages, which suggested that this viral expression system be stable.     

The three-dimensional structure of the bacterial virus MS2

The structure of the icosahedral bacteriophage MS2 has been determined to 3.3 A resolution by X-ray crystallography. The phase determination involved both molecular replacement at low resolution using a known structure and heavy-atom substitution. The coat protein has no structural similarity to that of any other known RNA virus.     

水稻条叶枯病毒云南分离物（RStV.Y）的纯化与理化特性分析

采用改进的水稻病毒纯化方法，以２００ｇ／Ｌ的蔗糖垫替代蔗糖密度梯度，从ＲＳｔＶ感染的水稻叶片中制备了病毒颗粒，电镜观察显示，ＲＳｔＶ为细丝状和分枝状结构，变性琼脂糖凝胶电泳分析分离纯化的病毒总ＲＮＡ得到４个大小不 同的病毒ＲＮＡ。     

利用根癌农杆菌介导的转化方法改良木霉菌

根癌农杆菌介导的转化系统在丝状真菌的研究中具有重要的意义。通过农杆菌介导,成功实现了丝状真菌绿色木霉菌(Trichoderma viride)遗传转化,转化率约为30～80个转化子／10^5个孢子。PCR检测和几丁质酶分析表明含有编码几丁质酶外源基因(Cli 113)的T-DNA已整合进木霉菌基因组中,而且转化子都能够稳定遗传。农杆菌介导的遗传转化方法具有转化率高、操作简便、遗传稳定等优点,在丝状真菌的遗传转化中具有重要的意义。     

基因重组型枯草芽孢杆菌芽孢表面展示技术与应用

枯草芽孢杆菌是一种好氧型革兰氏阳性益生菌,在营养匮乏的环境下,可形成具有强抗逆性的芽孢。其芽孢独特的结构和生理功能使得芽孢表面展示技术相较于其他表面展示技术具有多种优势,构建的重组芽孢不但易纯化、回收率高,而且安全性好。近年来,枯草芽孢杆菌芽孢表面展示技术得到迅猛发展,已成功利用CotB、CotC、CotG、CotZ、CotA、OxdD、CotE、CotZ、CgeA等多种锚定蛋白将外源蛋白或多肽展示在芽孢表面,并应用于工业化酶、口服疫苗和药物、大分子量多聚体蛋白的生产以及环境污染的生物治理等领域。本文首先介绍了芽孢展示系统整合策略,并重点阐述了基因重组型枯草芽孢杆菌芽孢展示技术中涉及的锚定蛋白以及该技术在各领域的应用与展望。     

In vivo competition between self peptides and foreign antigens in T-cell activation

Cytotoxic and helper T lymphocytes recognize foreign antigen in the form of short peptides associated with class I and class II major histocompatibility complex (MHC) molecules, respectively. A recent study of the three-dimensional structure of a class I MHC molecule revealed a cleft formed by the amino-terminal half of the protein, which could serve as the binding site for these peptides. Because an individual possesses only a limited set of different MHC molecules, each molecule of this set must have the ability to bind a large number of different peptides in order to ensure full immunocompetence. Thus, it can be anticipated that peptides with unrelated sequences compete for binding to the same MHC molecule, and, indeed, this has been shown to occur in vitro. We therefore decided to see whether such competition could also regulate the cell responses in vivo. We have found that a synthetic peptide corresponding to residues 46-62 of mouse lysozyme, although not immunogenic itself, effectively inhibits the priming for T-cell responses when injected into mice together with foreign protein or peptide antigens. The inhibition observed strictly correlates with the capacity of the competitor to bind to the particular MHC molecule presenting the foreign antigen, and its extent depends on the molar ratio between antigen and competitor.     

A coat subunit of Golgi-derived non-clathrin-coated vesicles with homology to the clathrin-coated vesicle coat protein beta-adaptin

Four high-molecular-weight proteins form the main subunits of the coat of Golgi-derived (non-clathrin) coated vesicles. One of these coat proteins, beta-COP, is identical to a Golgi-associated protein of relative mass 110,000 (110K) that shares homology with the adaptin proteins of clathrin-coated vesicles. This connection, and the comparable molecular weights of the coat proteins of Golgi-derived and clathrin-coated vesicles, indicates that they may be structurally related. The identification of beta-COP as the 110K protein explains the blocking of secretion by the drug brefeldin A.     

Filamentous phage integration requires the host recombinases XerC and XerD

Many bacteriophages and animal viruses integrate their genomes into the chromosomal DNA of their hosts as a method of promoting vertical transmission. Phages that integrate in a site-specific fashion encode an integrase enzyme that catalyses recombination between the phage and host genomes. CTX phi is a filamentous bacteriophage that contains the genes encoding cholera toxin, the principal virulence factor of the diarrhoea-causing Gram-negative bacterium Vibrio cholerae. CTX phi integrates into the V. cholerae genome in a site-specific manner; however, the approximately 6.9-kilobase (kb) CTX phi genome does not encode any protein with significant homology to known recombinases. Here we report that XerC and XerD, two chromosome-encoded recombinases that ordinarily function to resolve chromosome dimers at the dif recombination site, are essential for CTX phi integration into the V. cholerae genome. The CTX phi integration site was found to overlap with the dif site of the larger of the two V. cholerae chromosomes. Examination of sequences of the integration sites of other filamentous phages indicates that the XerCD recombinases also mediate the integration of these phage genomes at dif-like sites in various bacterial species.     

一种面向社区医疗微型输液监测系统的设计

研制一套面向社区医疗的微型输液监测系统,对输液进度进行实时监测,并在输液异常和输液结束时报警,以解决临床静脉输液方式不便,提高输液安全性和效率.采用光电传感技术和信号处理技术实现静脉输液液滴信号的可靠检测;利用单片机技术和数字显示技术实现输液量、输液速度的计数、显示与监控,实现无液报警和堵塞报警.另外,在系统中利用医院现有网络实现远程监测.最后,分析系统的临床应用情况,提出了存在的问题以及今后研究的重点.     

基于立体投影技术的虚拟现实显示系统

虚拟现实显示系统是虚拟现实中的关键组成部分。介绍虚拟现实显示系统三维立体显示技术中的立体投影技术,分析虚拟现实显示系统的常用形式——多通道环幕(立体)投影系统的主要构成,探讨虚拟现实显示系统在教学虚拟实验实训中的应用。     

两种胰蛋白酶酶解羊肌肉总蛋白样品的质谱分析

摘要: 目的比较国产和进口两种胰蛋白酶对蛋白质的酶解效果,为后续蛋白质组学稳定研究提供依据。方法用超声破碎法提取羊肌肉组织总蛋白,经两种胰蛋白酶酶解后液相色谱串联质谱检测酶解肽段,将结果上传蛋白质序列数据库,利用质谱分析鉴定方法分析比较两种胰蛋白酶的酶解效果,并借助生物信息学工具对所得数据进行分析。结果两种胰蛋白酶酶解同种蛋白质样品产生的肽段长度86%以上均为6-18 个氨基酸,适用于质谱检测。酶解后肽段产生的质量国产胰蛋白酶优于进口胰蛋白酶,国产胰蛋白酶比进口胰酶酶解可多鉴定到19% 的蛋白质和34%的肽段。结论进口、国产的胰蛋白酶在酶解蛋白质方面均可用于质谱检测前蛋白质的酶解消化。但国产胰蛋白酶价格明显低于进口胰酶,更具应用优势。本研究为评价胰蛋白酶酶解效果提供了一种有效、全面的研究方法。     

SEC21 is a gene required for ER to Golgi protein transport that encodes a subunit of a yeast coatomer.

Non-clathrin coated vesicles have been implicated in early steps of intercompartmental transport. A distinct set of coat proteins are peripherally associated with the exterior of purified mammalian intra-Golgi transport vesicles. The 'coatomer', a cytosolic complex containing a similar subunit composition to and sharing at least one subunit (beta-COP) with the coat found on vesicles, has been postulated to be the precursor of this non-clathrin coat. Here we describe the characterization of SEC21, an essential gene required for protein transport from the endoplasmic reticulum to the Golgi in the yeast Saccharomyces cerevisiae. The 105K product of this gene, Sec21p, participates in a cytosolic complex that we show to be a yeast homologue of the mammalian coatomer. These observations demonstrate that a non-clathrin coat protein plays an essential role in intercompartmental transport.     

'Coatomer': a cytosolic protein complex containing subunits of non-clathrin-coated Golgi transport vesicles

Golgi-derived coated vesicles contain a set of coat proteins of relative molecular mass 160,000 (Mr 160K; alpha-COP), 110K (beta-COP), 98K (gamma-COP) and 61K (delta-COP), and several smaller subunits. We have now identified and purified a cytosolic complex containing the same four coat proteins as those of Golgi transport vesicles. We term this complex the Golgi coat promoter or 'coatomer'. The coatomer also contains polypeptides of Mr 36K, 35K and 20K. It represents about 0.2% of soluble cytosolic protein. Gel filtration of unfractionated cytosol indicates that beta-COP resides exclusively in the coatomer complex. The complex seems to be a likely candidate for the unassembled precursor of Golgi coated vesicles, and its purification should help investigations of the role of coat proteins in membrane budding, for which it is necessary to use a refined cell-free system.