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1、细菌的磷酸转移酶系统 Bacteria are thrifty cells. They often live in inhospitable environments, and many live in places with no oxygen, so their options for generating energy are limited. So, bacteria have developed many clever ways of living off of whatever is available, and exploiting these resources to thei
2、r best advantage. The bacterial phosphotransferase system, often abbreviated as PTS, is a perfect example of both the opportunistic nature of bacterial life, and their thrifty use of resources. 注释： 细菌是种节俭的细胞生物体。他们通常都在恶劣的环境当中生存，甚至许多生存在没有氧气的地方，所以他们产生能量的方式选择非常有限。因此细菌自身培养了许多巧妙的方法以适应接触的任何环境，以及开发这些资源于自身以最
3、好的利用。细菌的磷酸转移酶系统，通常缩写为PTS，无论是对细菌生活的多机会自然环境，还是他们节俭使用的资源，都是一个完美的例子。Leading ：细菌中糖的磷酸转移酶功能发现In 1964, Kundig, Ghosh and Roseman reported the discovery of the PEP: sugar phosphotransferase system (PTS). Thirty years later, we find that the PTS functions not only as a sugar-phosphorylating system, but also
4、as a complex protein kinase（复合蛋白激酶） system that regulates（调节） a wide variety of metabolic（新陈代谢的） processes and controls the expression of numerous（大量） genes. As a result of recent operon- and genome-sequencing projects, novel新的 PTS protein-encoding编码 genes have been discovered, most of which have ye
5、t to be functionally defined. Some of them appear to be involved in cellular细胞的 processes distinct from those recognized previously先前的. Fundamental aspects of past and current PTS research are briefly reviewed, and recent advances增长 are integrated整合 into conceptual pictures that provide guides for f
6、uture research. How Phosphotransferase System-Related Protein Phosphorylation Regulates Carbohydrate Metabolism（糖类新陈代谢系统） in Bacteria 蛋白的磷酸化及去磷酸化状态在分解物代谢阻遏中起关键作用。PTS系统是运载体家族中的转位分子，在原核生和古细菌中广泛存在。大肠杆菌主要通过PEPsugar PTS以集团转移方式进行葡萄糖的摄取，PTS包括EI，HPr，EII。前两者为胞质可溶型蛋白，无底物识别特异性。分别由pstI，pstH操纵子编码，后者多为蛋白复合体，对碳水化合
7、物具有识别特异性,可特异性识别和转运底物分子，E.coli编码约20种Es，涉及20多种不同碳化物磷酸化转运。Hpr: histidine-containing phosphocarrier protein含组氨酸的磷酸载体蛋白 EI：extract(获得) the phosphate from PEP and adds it to the carrier protein, HPr.EII：分为EIIA,EIIB,EIIC类别，有时EIIC又会连带上EIID磷酸转移酶系统蛋白磷酸转移酶系统蛋白-蛋白复合体的三维结构蛋白复合体的三维结构 PTS的的作用过程作用过程：EI先从先从PEP处获得磷酸基
8、处获得磷酸基团，并将其加载到载体团，并将其加载到载体蛋白蛋白HPr上，然后载体蛋上，然后载体蛋白将磷酸基团传递给整白将磷酸基团传递给整个系列当中相对应不同个系列当中相对应不同的转运蛋白。磷酸基团的转运蛋白。磷酸基团在几种蛋白当中穿梭，在几种蛋白当中穿梭，从从HPr移动到移动到EIIA，再到，再到EIIB ，最终到达处在最终到达处在EIIC（有时会带上一个额（有时会带上一个额外的链外的链EIID）当中的葡萄）当中的葡萄糖。每个转运蛋白由糖。每个转运蛋白由EII蛋白自身的各个集成物蛋白自身的各个集成物组成，有时会作为隔离组成，有时会作为隔离蛋白，有时又会在一个蛋白，有时又会在一个长链蛋白质中作为一
9、连长链蛋白质中作为一连串相互连结的结构区域串相互连结的结构区域磷酸化的HPr是一个所有PTS中EII的磷酸通用供体。这个磷酸转移活性伴随着从PTS系列的通用磷酸转移部分到葡萄糖特异的那条途径。而葡萄糖特异的载体（IIAGlc）这个蛋白不仅作为葡萄糖转移过程中的中间体，同时也作为非PTS通透酶和腺苷酸环化酶的调节者。HPrIIAGlc复合体的结构是采用同位素标记蛋白质的组合，利用多维 异核NMR光谱技术解析的。 Carbohydrate transport and phosphorylation by the PTS and their coupling to glycolysis. Carbo
10、hydrates are transported and concomitantly phosphorylated by the PTS. The phosphorylated carbohydrate feeds into glycolysis, normally at the glucose-6-P or fructose-6-P level. Two phosphoenolpyruvate molecules are usually formed in glycolysis, one of which is used to drive the transport and initial
11、phosphorylation of the carbohydrate. As a result, the phosphorylation state of the PTS proteins depends on both the concentration of extracellular carbohydrates and the ratio of internal phosphoenolpyruvate and pyruvate. Abbreviations for enzymes (in boldface type) are as follows: Pgi, phosphoglucos
12、e isomerase; Pfk, phosphofructokinase; Fba, fructose-1,6-bisphosphate aldolase; Tpi, triose-phosphate isomerase; Gap, glyceraldehyde-3-phosphate dehydrogenase; Pgk, phosphoglycerate kinase; Pgm, phosphoglycerate mutase; Eno, enolase; Pyk, pyruvate kinase. 醛糖代谢PTS作用机制作用机制Self-priming Pump 自吸泵（能量）The
13、phosphotransferase system is particularly energy-efficient when compared to many of the other transport systems in the cell. Many transporters use ATP to power the import of nutrients, but PTS transporters also add a phosphate group to them at the same time. Instead of ATP, a molecule of PEP is used
14、 to power激活激活 the PTS reaction and provide the phosphate. This pre-phosphorylation of sugars糖的磷酸前体物糖的磷酸前体物 primes指指导导them for entry into the energy production pathways.Harvesting Resources 收获资源The phosphotransferase system is built around a collection of specific transporters that import resources i
15、nto the cell. PSI researchers have recently revealed the structure of one of these transporters, which imports a disaccharide双糖双糖. Typical bacterial cells make many similar transporters (E. coli has at least 15) that all stand ready to import whatever sugars are available. A complex regulatory netwo
16、rk decides which transporters are expressed and used at any given time.PST系统是一些特定运输物组建的集合体，这些运输物会向系统是一些特定运输物组建的集合体，这些运输物会向细胞中输入资源。细胞中输入资源。PSI研究者最近发现了这些运输物之一结构，研究者最近发现了这些运输物之一结构，此结构是向细胞内输入双糖。典型的细菌细胞有许多相似的此结构是向细胞内输入双糖。典型的细菌细胞有许多相似的转移物转移物(E. coli 至少至少15），无论糖类是否便于利用他们都时），无论糖类是否便于利用他们都时刻做好准备向内输入。一个刻做好准备向
17、内输入。一个复杂的调控系统网络决定着在特复杂的调控系统网络决定着在特定时间中哪一种转运物被表达或被利用。定时间中哪一种转运物被表达或被利用。Modular模块化，单元化ReactionThe modular nature of the EI and EII proteins allows the same energy production machinery to power many different sugar transporters. PSI researchers have determined the structures of several different forms
18、of the EIIB protein from different organisms and from different sugar transport complexes.研究方法研究方法对于包含在通过PTS进行磷酸转移的过程以及PTS蛋白参与调控过程的机制的理解在很大程度上是通过蛋白组分的相互作用的种类的三维结构的可视化来实现的。人们已经利用X衍射晶体学和NMR（核磁共振）对PTS的单个的蛋白（酶I、HPr、IIA）进行了广泛的特征分析。然而，除了甘油激酶IIAGlc复合体，没有一个PTS蛋白和其他组分或者和调控配伍的复合体被成功的结晶。核磁共振（NMR）光谱学已经成功地被人们用于解决蛋白蛋白复合体的结晶中遇到的问题。酶I和HPr之间以及HPr和IIAGlc（葡萄糖特异的载体）之间的氨基末端结构域的三维解已经成功地得到。 PTS的生理意义：此系统对于菌体具有以下的生理意义生理意义： 碳水化合物运转和代谢，分解物代谢阻遏 ，碳源储备，协调碳氮代谢平衡。 OVER _
