Crystal structure of enteropathogenic Escherichia coli intimin-receptor complex

Intimin and its translocated intimin receptor (Tir) are bacterial proteins that mediate adhesion between mammalian cells and attaching and effacing (A/E) pathogens. Enteropathogenic Escherichia coli (EPEC) causes significant paediatric morbidity and mortality world-wide. A related A/E pathogen, enterohaemorrhagic E. coli (EHEC; O157:H7) is one of the most important food-borne pathogens in North America, Europe and Japan. A unique and essential feature of A/E bacterial pathogens is the formation of actin-rich pedestals beneath the intimately adherent bacteria and localized destruction of the intestinal brush border. The bacterial outer membrane adhesin, intimin, is necessary for the production of the A/E lesion and diarrhoea. The A/E bacteria translocate their own receptor for intimin, Tir, into the membrane of mammalian cells using the type III secretion system. The translocated Tir triggers additional host signalling events and actin nucleation, which are essential for lesion formation. Here we describe the the crystal structures of an EPEC intimin carboxy-terminal fragment alone and in complex with the EPEC Tir intimin-binding domain, giving insight into the molecular mechanisms of adhesion of A/E pathogens.     

Distributed implementation of the genetic double-branch structure in Escherichia coli

Because of the simplicity of cells, the key to building biological computing systems may lie in constructing distributed systems based on cell-cell communication. Guided by a mathematical model, in this study we designed, simulated, and constructed a genetic double-branch structure in the bacterium Escherichia coli. This genetic double-branch structure is composed of a control cell and two reporter cells. The control cell can activate different reporter cells according to the input. Two quorum-sensing signal molecules, 3OC12- HSL and C4-HSL, form the wires between the control cell and the reporter cells. This study is a step toward scalable biological computation, and it may have many potential applications in biocomputing, biosensing, and biotherapy.     

高斯整环的商环中一般元素的表达形式

利用同余和等价关系得出了高斯整环的商环中一般元素的表达式及高斯整环的商环的同构形式     

Crystal structure of the CusBA heavy-metal efflux complex of Escherichia coli

Gram-negative bacteria, such as Escherichia coli, expel toxic chemicals through tripartite efflux pumps that span both the inner and outer membrane. The three parts are an inner membrane, substrate-binding transporter; a membrane fusion protein; and an outer-membrane-anchored channel. The fusion protein connects the transporter to the channel within the periplasmic space. A crystallographic model of this tripartite efflux complex has been unavailable because co-crystallization of the various components of the system has proven to be extremely difficult. We previously described the crystal structures of both the inner membrane transporter CusA and the membrane fusion protein CusB of the CusCBA efflux system of E. coli. Here we report the co-crystal structure of the CusBA efflux complex, showing that the transporter (or pump) CusA, which is present as a trimer, interacts with six CusB protomers and that the periplasmic domain of CusA is involved in these interactions. The six CusB molecules seem to form a continuous channel. The affinity of the CusA and CusB interaction was found to be in the micromolar range. Finally, we have predicted a three-dimensional structure for the trimeric CusC outer membrane channel and developed a model of the tripartite efflux assemblage. This CusC(3)-CusB(6)-CusA(3) model shows a 750-kilodalton efflux complex that spans the entire bacterial cell envelope and exports Cu I and Ag I ions.     

大肠杆菌NADP特异性谷氨酸脱氢酶基因的克隆及其在大肠杆菌中的高效表达与纯化

谷氨酸脱氢酶是生物体内最主要的氧化脱氨基酶类，为了进一步研究其功能，我们以大肠杆菌DH5α菌株基因组DNA为模板和相应的寡聚脱氧核苷酸为引物，进行PCR扩增大肠杆菌NADP特异性谷氨酸脱氢酶基因(NADP-specific glutamate dehydrogenase，gdhA gene)，将所得DNA片断连接到质粒pUC18上，转化大肠杆菌DH5α，进行蓝白筛选和酶切鉴定，经测序证明序列正确无误后将gdhA基因连接到表达载体pTrcHisC上，在大肠杆菌BL21(DE3)中表达，经SDS-PAGE和双波长扫描分析，确定大肠杆菌谷氨酸脱氢酶在大肠杆菌中表达时以包涵体的形式存在，未能检测到可溶性蛋白的表达，表达量可达菌体总蛋白的15％以上．     

具有对合的四元素体上斜Hermitian矩阵的距离与算术距离

设R是一个具有对合的四元素体,Hn(R)表示R上所有的斜Hermitian矩阵构成的集合,讨论了Hn(R)上的距离与算术距离,给出了距离与算术距离相等的一个充要条件:若ゅ妒为Hn(R)到自身的双射,则ゅ与ゅ-1保持粘切当且仅当ゅ为保持算术距离的映射.     

Antibodies from Escherichia coli

Use of Escherichia coli as an expression host has opened up new possibilities in antibody research and its applications. It greatly facilitates rational engineering and random mutagenesis.     

大肠杆菌基因组的组构

以１９９３年４月为止的ＤＮＡ序列资料为依据，讨论了一年来大肠杆菌基因的研究进展，并以日本和美国科学家分别完成的两大片段的序列资料为中心，评述了大肠杆菌基因组的组成特点及其生物学意义．     

体上矩阵的减序及其性质

定义了体上矩阵减序,将减序推广到任意有单位元的环上矩阵,并对其性质作了一个简明的讨论.应用体上矩阵理论,证明了体上矩阵减序的5个充要条件.     

TL-带算商环及其直积结构

引入了TL-带算商环的概念,给出了TL-带算环的同态基本定理,证明了两个TL-带算子环(理想)的直积还是TL-带算子环(理想),并讨论了TL-带算商环的直积结构.T表示完备的Brouwerian格L上任意给定的无穷∨-分配t-模.