Antimicrobial activity in the skin of the channel catfish Ictalurus punctatus: characterization of broad-spectrum histone-like antimicrobial proteins

Three antibacterial proteins were isolated from acid extracts of channel catfish (Ictalurus punctatus) skin by cation exchange chromatography and reverse-phase high-pressure liquid chromatography. The molecular masses of the proteins were 15.5, 15.5 and 30 kD as determined by SDS-polyacrylamide gel electrophoresis. Mass spectrometry, amino acid composition and amino acid sequence data suggest that the most abundant protein is closely related to histone H2B. The H2B-like protein was inhibitory to Aeromonas hydrophila and Saprolegnia spp., which are important bacterial and fungal pathogens of fish. These findings suggest that histones may be important defensive molecules in fish. Received 22 December 1997; received after revision 5 March 1998; accepted 5 March 1998     

Emerging connections between DNA methylation and histone acetylation

Modifications of both DNA and chromatin can affect gene expression and lead to gene silencing. Evidence of links between DNA methylation and histone hypoacetylation is accumulating. Several proteins that specifically bind to methylated DNA are associated with complexes that include histone deacetylases (HDACs). In addition, DNA methyltransferases of mammals appear to interact with HDACs. Experiments with animal cells have shown that HDACs are responsible for part of the repressive effect of DNA methylation. Evidence was found in Neurospora that protein acetylation can in some cases affect DNA methylation. The available data suggest that the roles of DNA methylation and histone hypoacetylation, and their relationship with each other, can vary, even within an organism. Some open questions in this emerging field that should be answered in the near future are discussed.     

Hydroxyproline-rich glycoproteins in plant reproductive tissues: structure, functions and regulation

The plant reproductive process of pollination involves a series of interactions between the male gametophyte (the pollen grain or pollen tube) and extracellular matrix (ECM) molecules secreted by different cell types along the pollen tube growth pathway in the female organ, the pistil. These interactions are believed to signal and regulate the pollen tube growth process to effect successful delivery of the sperm cells to the ovules where fertilization takes place. Hydroxyproline-rich glycoproteins secreted by plant cells are believed to play a broad range of functions, ranging from providing structural integrity to mediating cell-cell interactions and communication. The pistil and pollen tube ECM is enriched in these highly glycosylated proteins. Our discussions here will focus on a number of these proteins for which most information has been available, from Nicotiana tabacum, its self-incompatible relative N. alata, and Zea mays. In addition, the regulation of the synthesis and glyco-modification of one of these proteins, TTS (transmitting tissue-specific) protein from N. tabacum will be discussed in the light of how differential glycosylation may be used to regulate molecular interactions within the ECM.     

Structural genomics for membrane proteins

Structure-based drug discovery has proven useful in improving and shortening the drug development process. The approach of structural genomics to study a large number of targets in parallel has been commonly applied to protein families and even whole genomes. Paradoxically, although membrane proteins represent the largest type of drug targets, up to 70% today, determination of their structure has been modest compared to that of soluble proteins. Because membrane proteins are important for drug discovery an emphasis has been placed on developing technologies and methods to determine membrane protein structures. Several structural genomics initiatives have been established, focusing on the structural biology of membrane proteins. Received 31 May 2006; received after revision 5 July 2006; accepted 9 August 2006     

The role of kinesin, dynein and microtubules in pancreatic secretion

The regulated secretion of pancreatic zymogens depends on a functional cytoskeleton and intracellular vesicle transport. To study the dynamics of tubulin and its motor proteins dynein and kinesin during secretion in pancreatic acinar cells, we infused rats with 0.1 μg/kg/h caerulein. Electron and fluorescence microscopy detected neither dynein nor kinesin at the apical secretory pole, nor on the surface of mature zymogen granules. After 30 min of secretagogue stimulation, kinesin and the Golgi marker protein 58 K were reallocated towards the apical plasma membrane and association of kinesin with tubulin was enhanced. Disruption of acinar cell microtubules had no effect on initial caerulein-induced amylase release but completely blocked secretion during a second stimulus. Our results suggest that mature zymogen granule exocytosis is independent of intact microtubules, kinesin and dynein. However, microtubule-dependent mechanisms seem to be important for the replenishment of secretory vesicles by redistribution of Golgi elements towards the apical cell pole. J. Schnekenburger and I.-A. Weber have contributed equally to this work.     

Regulatory mechanisms of mitogen-activated kinase signaling

MAP kinases (MAPKs) are evolutionarily conserved regulators that mediate signal transduction and play essential roles in various physiological processes. There are three main families of MAPKs in mammals, whose functions are regulated by activators, inactivators, substrates and scaffolds, which together form delicate signaling cascades in response to different extracellular or intracellular stimulation. MAPK signaling is tightly regulated so that optimal biological activities are achieved and health is maintained. However, how the specificity of the signaling flow along each cascade is achieved is still relatively unclear. In this review, we summarize recent advances in understanding the regulation of MAPK cascades and the roles of MAP kinases and their regulators in development and in immune responses. Received 11 January 2007; received after revision 31 May 2007; accepted 5 July 2007     

有机溶剂沉淀法去除子宫内膜癌血清高丰度蛋白的比较研究

建立了一种简便有效、成本低廉的去除子宫内膜癌血清高丰度蛋白的方法．运用3种不同的有机溶剂（不同体积倍数）处理子宫内膜癌血清样品,SDS．PAGE电泳检测去除高丰度蛋白．结果表明：不同的有机溶剂沉淀法都能去除血清样品中绝大部分的高、中丰度蛋白,但低丰度蛋白质保留、减弱及丢失的现象不一．用1倍体积乙腈可有效去除子宫内膜癌血清样品中的绝大部分高丰度蛋白,同时保留较多的小分子量蛋白．     

史氏鲟（Acipenser schrenckii）两种促性腺激素β亚基的原核表达

 采用遗传工程方法,重组表达史氏鲟两种促性腺激素β亚基蛋白。选用原核表达载体pET－22b(+),分别插入史氏鲟GtHⅠ&;Ⅱβ亚基成熟肽cDNA序列,构建成C端含有6个组氨酸(6-His)融合蛋白标签的表达质粒;分别转化大肠杆菌表达菌株BL21（DE3）并诱导表达2个基因。SDS-聚丙烯酰胺凝胶电泳显示重组融合蛋白相对分子质量分别为：GtHⅠβ亚基大约14 000,GtHⅡβ亚基15 000左右。分别用抗6个组氨酸融合标签的单克隆抗体及兔抗鲟鱼GTH多克隆抗体对2个表达蛋白进行Western Blot分析,结果显示重组蛋白表达正确且有较高的免疫活性。GTHⅠβ重组蛋白在2 h就有明显的表达,6 h后随着时间增加表达量不再增加;25 ℃诱导重组蛋白产量比37 ℃诱导产量低。获得的重组蛋白质将可用于建立鲟鱼GtH的放射免疫测定方法。     

线粒体膜间隙蛋白质释放与细胞凋亡研究进展

近年来,国内外有关线粒体和肿瘤的关系研究的越来越多,开发与线粒体相关的新型药物并诱导肿瘤细胞凋亡逐渐成为热点.该文主要综述了近年来关于几种线粒体膜间隙蛋白质在细胞凋亡中的作用和由线粒体中释放的可能机制及其在肿瘤药物治疗中的最新进展,指出线粒体膜间隙蛋白质在诱导肿瘤细胞凋亡中具有重要作用.     

不同年龄小白鼠全脑不溶蛋白凝胶等电聚焦比较分析

用含有酵母tRNA和小白鼠氨酰tRNA合成酶的异源检测体系,测定到小白鼠脑组织的氨酰tRNA合成酶,运载氨基酸tRNA的活力,随小白鼠年龄和不同氨基酸而异,是否小白鼠全脑的不溶蛋白,也随年龄而有变化。作者用聚丙烯酰胺凝胶等电聚焦技术,对小白鼠全脑的不溶蛋白进行了测定。根据凝胶等电聚焦图谱证实,不同年龄小白鼠全脑不溶蛋白的主要组分是相似的,但在530毫微米波长处的吸光值有明显的差异。这种变化结果是否与该组分的氨基酸组成及其含量有关,有待进一步探究。