Chemo‐Enzymatic Synthesis of Fluorescent Rab 7 Proteins: Tools to Study Vesicular Trafficking in Cells

The N ‐methylanthraniloylisoprenoid diphosphate derivatives 1 and 2 bind to RabGGTase II and are enzymatically transferred to Rab 7 (the Rab proteins are small G‐proteins that control events of docking and fusion of intracellular vesicles). The fluorescent Rab 7 proteins thus obtained may become important tools for further biological studies on vesicular trafficking in cells.     

Chemoenzymatic Synthesis of a Characteristic Glycophosphopeptide from the Transactivation Domain of the Serum Response Factor

Glycopeptides, phosphopeptides, and glycophosphopeptides can be synthesized efficiently by a strategy based on a combination of suitable enzyme-labile protecting groups. Thus, probes for biological studies can be accessed. An example is the glycosylated and phosphorylated heptapeptide 1 from the transactivation domain of the human serum response factor, which contains an additional biotin label for detection with streptavidin.     

应力刺激在植物细胞防卫反应中的作用

在病原菌与植物初步接触并企图定植期间,有一系列的识别活动,其中包括物理学和生化识别等．二者的相互关系,将直接影响以后的侵染．在病原真菌侵染过程中,不仅对植物细胞有一个酶解的过程,还有一个物理挤压的过程．后者的应力刺激几乎总是能够引起细胞壁相关的防卫反应,诸如细胞外超氧化物的产生和胼胝质的沉积等．化学信号和力学信号诱导的有机结合才能引发完整的细胞防卫反应．和哺乳动物细胞相似,植物细胞对于力学信号的感知和传导依赖于细胞壁和细胞膜之间的粘附。该粘附是由包含RGD（Arg-Gly-Asp）序列多肽特异介导的,并且该粘附为植物细胞壁相关防卫基因表达所必需．     

The Crystal Structure of a Potassium Channel— A New Era in the Chemistry of Biological Signaling

The similarity to crown ethers is apparent when the arrangement of the oxygen atoms of the carbonyl groups of the protein backbone in the structure of the potassium channel (see schematic drawing of a section of the structure) found in the bacterium Streptomyces lividans is considered. This particular part of the channel pore acts as the selectivity filter, with the permeability of the channel for K⁺ being as much as 10 000 times greater than for the Na⁺ ion. In fact, in this area of the structure two K⁺ ions are located, a feature that enables high flux through the channel.     

TAT-SOD融合蛋白的跨膜转导性质的研究

探讨了融合蛋白TAT-SOD的跨膜转导特性.实验结果表明:非变性的TAT-SOD也可以不受细胞种类限制,突破质膜屏障,显著提高L02、A375、Hela细胞的胞内SOD的活力;TAT-SOD的这种跨膜转导有明显的浓度、时间依赖关系,随着浓度和时间的增加而增加;在TAT跨膜转导SOD过程中,TAT-SOD首先黏附到细胞膜上,黏附量随TAT-SOD浓度的提高而明显增加,随作用时间的延长虽然也有增加,但是在30 min内迅速达到一个较高的水平,其后增加的趋势极为缓慢.细胞紫外线辐射防护试验表明,320 U/mL的TAT-SOD对细胞的保护率约为野生型SOD的5倍.试验结果说明,TAT-SOD具有明显的跨膜转导能力,可提高SOD的生物利用率.     

运动细胞初始极化阶段胞内信号分子双向积聚的分子机制及动态数值模拟

真核细胞（Eukaryotes）,如盘基网柄菌细胞（Dictyo stelium）和白细胞（Leukocyte）等,受到前方传来的外信号刺激后,胞内物质发生两种方向相反的运动：胞质中与质膜结合的磷酸激酶PI3K及其在质膜上的生成物磷脂酰肌醇-3,4,5-三磷酸PI（3,4,5）P3以向前扩散的方式积聚到前沿;而胞质中与质膜结合的磷酸酶PTEN及其在质膜上的生成物磷脂酰肌醇-4,5-双磷酸PI（4,5）P2以向后扩散的方式积聚到质膜的后边.通过这种＂双向积聚＂,细胞形成头部和尾部,并在前沿生出伪足,完成初始极化.本文根据已知的实验,分析了＂双向积聚＂的分子机制,建立了相应的数学模型,通过数值模拟加以分析.以胞内被激活的小G蛋白（Rac）为触发信号,其梯度与外信号场的梯度一致;PI3K和PTEN作为调控因子,PI（3,4,5）P3和PI（4,5）P2作为标识细胞极化的信号分子,它们的浓度变化由一组耦合的非稳态二维反应-扩散方程描述.该反应-扩散体系源项中包含：PI（3,4,5）P3对PI3K,PI（4,5）P2对PTEN的识别和结合过程,是由蒙特-卡诺（Monte-Carlo）法处理;质膜结合态PI3K和PTEN对PI（3,4,5）P3和PI（4,5）P2施加的酶催化作用,由Michaelis-Menten动力学过程描述.反应-扩散方程组采用格子Boltzmann方法进行数值求解.数值试验显示,产生＂双向积聚＂的关键是受外信号梯度刺激后的胞内信号分子相互激发或抑制所形成的正反馈或负反馈回路：给细胞质膜头部一个较高的Rac激活率,Rac→PI3K？PI（3,4,5）P3将形成短程正反馈回路（亦即＂局部激励＂）,引起PI3K和PI（3,4,5）P3快速在细胞头部积聚;头部PI（3,4,5）P3增多,限制了PTEN与PI（4,5）P2结合,使得PI（3,4,5）P3？PTEN→PI（4,5）P2形成长程负反馈回路（亦即＂全局抑制＂）;引起PTEN和PI（4,5）P2慢慢在细胞尾部积聚.同时发现,PI3K和PTEN含量对细胞极化有明显的影响,并存在使细胞正确极化的最佳值.     

Identification and primary genetic analysis of Arabidopsis stomatal mutants in response to multiple stresses

In response to variable environmental conditions, guard cells located in the leaf epidermis can integrate and cope with a multitude of complicated stimuli, thereby making stomata in an appro- priate state. However, many signaling components in guard cell signaling remain elusive. In our laboratory, a tool for non-invasive remote infrared thermal images was used to screen an ethyl methane sulfonate-mutagenized population for Arabidopsis stomatal response mutants under multiple stresses (ABA, H2O2, CO2, etc.). More than forty "hot" or "cold" mutants were isolated (above or below 0.5℃ in con- trast to normal plantlets). Identification and primary genetic analysis of these mutants show that they are monogenic recessive mutations and there exist distinct difference in stomata apertures compared to wild type. These mutants in response to various environmental stresses and hormones were comprehen- sively investigated, which enables us to further un- derstand the cross-talk in different signal transduction pathways.     

应力方向对内皮细胞力学传递和功能的影响

剪切力可经由应力感受、信息传递和基因与蛋白质的表达来调控血管内皮细胞的功能。层流剪切力会导致单核细胞趋化蛋白质(MCP-1)及多种增生基因的迅速上调。但有特定方向的持久层流剪切力会使MCP-1及增生基因与蛋白下调, 同时并上调抑制内皮细胞增生的基因与蛋白。复杂的流型没有什么固定的方向,会使MCP-1及增生基因持续上调,因而增加单核细胞的侵入及内皮细胞的分裂及凋亡。在动脉的直管部分,层流剪切力有特定的方向,因此有抗动脉粥样硬化的作用。在动脉分支部位,复杂的流型有促使动脉粥样硬化的作用。所以,应力的方向对内皮细胞在正常及疾病时的功能有重要影响。     

Detection of Protein S‐Sulfhydration by a Tag‐Switch Technique

Protein S‐sulfhydration (forming ‐S‐SH adducts from cysteine residues) is a newly defined oxidative posttranslational modification and plays an important role in H₂S‐mediated signaling pathways. In this study we report the first selective, “tag‐switch” method which can directly label protein S‐sulfhydrated residues by forming stable thioether conjugates. Furthermore we demonstrate that H₂S alone cannot lead to S‐sulfhydration and that the two possible physiological mechanisms include reaction with protein sulfenic acids (P‐SOH) or the involvement of metal centers which would facilitate the oxidation of H₂S to HS^..