同源α-螺旋结构蛋白质Im7和Im9的变性及折叠特性的研究

Im7和Im9是具有相似三维空间结构的同源蛋白质分子，这两种蛋白质的一级序列中有60％的残基成分相同，研究结果显示，Im7和Im9分子具有不同的稳定性和经历不同的折叠途径，为解释有关的实验事实，利用吸附反应动力学方法，分析了Im7和Im9两种蛋白质的变性过程和重折叠过程，结合Im7蛋白质和Im9蛋白质所具有的空间结构特性，对Im7和Im9蛋白质具有不同稳定特性和折叠途径存在差异的原因做了进一步的讨论和解释。     

Hormone-induced subcellular redistribution of trimeric G proteins

Trimeric guanine nucleotide-binding proteins (G proteins) function as the key regulatory elements in a number of transmembrane signaling cascades where they convey information from agonist-activated receptors to effector molecules. The subcellular localization of G proteins is directly related to their functional role, i.e., the dominant portion of the cellular pool of G proteins resides in the plasma membrane. An intimate association of G protein subunits with the plasma membrane has been well known for a long time. However, results of a number of independent studies published in the past decade have indicated clearly that exposure of intact target cells to agonists results in subcellular redistribution of the cognate G proteins from plasma membranes to the light-vesicular membrane fractions, in internalization from the cell surface into the cell interior and in transfer from the membrane to the soluble cell fraction (high-speed supernatant), i.e., solubilization. Solubilization of G protein α subunits as a consequence of stimulation of G protein-coupled receptors (GPCRs) with agonists has also been observed in isolated membrane preparations. The membrane-cytosol shift of G proteins was detected even after direct activation of these proteins by non-hydrolyzable analogues of GTP or by cholera toxin-induced ADP-ribosylation. In addition, prolonged stimulation of GPCRs with agonists has been shown to lead to down-regulation of the relevant G proteins. Together, these data suggest that G proteins might potentially participate in a highly complex set of events, which are generally termed desensitization of the hormone response. Internalization, subcellular redistribution, solubilization, and down-regulation of trimeric G proteins may thus provide an additional means (i.e., beside receptor-based mechanisms) to dampen the hormone or neurotransmitter response after sustained (long-term) exposure. Received 31 August 2001; received after revision 31 October 2001; accepted 7 November 2001     

The role of perireceptor events in vertebrate olfaction

The perception of odours and pheromones is mediated by small soluble carrier proteins that belong to the family of lipocalins. Those secreted by the nasal mucosa are called odorant-binding proteins (OBPs) for their binding activity towards volatile compounds. Proteins of similar structure, which we call pheromone-binding proteins (PBPs), help to deliver volatile pheromones in the environment. They are present in high concentration in biological fluids, such as urine, saliva and vaginal discharge, involved in chemical communication between conspecifics. Several subclasses of OBPs have been identified in the same animal species, each best related to a particular group of PBPs. Such similarities, together with anatomical and behavioural evidence, suggest that OBPs may be involved in the perception of pheromones.     

上海四膜虫细胞膜和纤毛的蛋白质研究

以丰富有机培养基恒温无菌培养的上海四膜虫（ＴｅｔｒａｈｙｍｅｎａｓｈａｎｇｈａｉｅｎｓｉｓＳｌ）为实验材料，分别收集对数生长期和衰老期的四膜虫，用Ｎｏｚａｗａ等人［１］法制备细胞膜和纤毛样品，并按Ｌａｅｍｍｌｉ［２］法进行凝胶电泳，并扫描分析，还采用４％～２５％梯度凝胶电泳．结果为：（１）对数期的膜和纤毛样品的蛋白带，在相同的峰面积０．２ｍｍ２以上计算分别为３７和４０条，相应地比衰老期的膜和纤毛样品的蛋白带４７和４５条要少；（２）两种生理状态的纤毛样品在高分子区域蛋白带比膜样品多，并具有膜样品没有的３６０×１０３，３５５×１０３，３４５×１０３，３４０×１０３和３３０×１０３的蛋白带，而缺少膜含有的２５０×１０３，２００×１０３和１８０×１０３等蛋白带；（３）两种生理状态的纤毛和膜样品内部有明显的差别，即使具有相同的蛋白带，其含量也有显著不同．这些差别对于研究细胞衰老的分子机理有重要意义．     

Small,novel proteins from the mistletoe <Emphasis Type="Italic">Phoradendron tomentosum</Emphasis> exhibit highly selective cytotoxicity to human breast cancer cells

Four novel proteins (phoratoxins C–F) have been isolated from the North American mistletoe Phoradendron tomentosum. The amino acid sequences of these phoratoxins were determined unambiguously using a combination of Edman degradation and trypsin enzymatic digestion, and by electrospray ionization tandem mass spectrometry sequencing. Phoratoxins C, E and F consist of 46 amino acid residues; and phoratoxin D of 41. All proteins had six cysteines, similar to the earlier described phoratoxins A and B, which are thionins. The cytotoxicity of each protein was evaluated in a human cell line panel that represented several cytotoxic drug-resistance mechanisms. For the half-maximal inhibitory concentrations (IC₅₀ values) of the different cell lines in the panel, correlation with those of standard drugs was low. The most potent cytotoxic phoratoxin C was further tested on primary cultures of human tumor cells from patients. The solid tumor samples from breast cancer cells were 18 times more sensitive to phoratoxin C than the tested hematological tumor samples. Received 30 September 2002; received after revision 28 October 2002; accepted 7 November 2002 RID="*" ID="*"Corresponding author.     

JWA, a novel microtubule－associated protein, regulates homeostasis of intracellular amino acids in PC12 cells

Our previous studies demonstrated that JWA,a novel retinoic acids responsive and cytoskeleton related gene, is associated with cell differentiation and apoptosis. In the present study, to elucidate if the JWA is a novel kind of microtubnle-associated proteins (MAPs) and functiona llylink to microtubule, we first successfully identified JWA from the physically purified MAPs complex of rat braint issues. The results of co-immunoprecipitation, gene transfection and immunofluorescence microscopy assays from HBE and NIH3T3 cells provide strong evidence for a linkage between JWA and β-tubulin. In general, JWA is stably binding to β-tubulin whenever microtubule is polymerized or not,and it may be critical to the mitosis process. In addition, by use of the antisense oligonucleotides technique, we also showed that JWA is a negative modulator on intracellular amino acids in PC12 cells. Further analysis indicated that JWA selectively regulates both taurine, an inhibitory aminoacid, and glutamate, an excitatory amino acid. In conclusion,JWA is not only structurally associated, but also a novel functional MAP.     

分子印迹技术在多肽、蛋白质分离中的应用

介绍了分子印迹聚合物(Molecularly Imprinted Ploymer,MIP)在分离生物大分子——多肽、蛋白质等领域中的应用进展，及其发展前景。