• 主题
高级搜索  >
历史搜索 清空历史

您现在的位置：首页>美国卫生研究院文献>Journal of Molecular Microbiology and Biotechnology

期刊信息

  • 期刊名称：

    -

  • 刊频： 8 no. a year, 2003-
  • NLM标题：
  • iso缩写： -
  • ISSN： -

年度选择

更多>>

  • 排序：
  • 显示：
  • 每页：
全选（0）
<1/2>
共37条结果
  • 1.

    【2hr】Comparative Analyses of Transport Proteins Encoded within the Genomes of Bdellovibrio bacteriovorus HD100 and Bdellovibrio exovorus JSS

    包量

    机译 Bdellovibrio bacteriovorus HD100和Bdellovibrio exovorus JSS基因组内编码的转运蛋白的比较分析
    摘要：Bdellovibrio, δ-proteobacteria, including B. bacteriovorus (Bba) and B. exovorus (Bex), are obligate predators of other Gram-negative bacteria. While Bba grows in the periplasm of the prey cell, Bex grows externally. We have analyzed and compared the transport proteins of these 2 organisms based on the current contents of the Transporter Classification Database (TCDB; ). Bba has 103 transporters more than Bex, 50% more secondary carriers, and 3 times as many MFS carriers. Bba has far more metabolite transporters than Bex as expected from its larger genome, but there are 2 times more carbohydrate uptake and drug efflux systems, and 3 times more lipid transporters. Bba also has polyamine and carboxylate transporters lacking in Bex. Bba has more than twice as many members of the Mot-Exb family of energizers, but both may have energizers for gliding motility. They use entirely different types of systems for iron acquisition. Both contain unexpectedly large numbers of pseudogenes and incomplete systems, suggesting that they are undergoing genome size reduction. Interestingly, all 5 outermembrane receptors in Bba are lacking in Bex. The 2 organisms have similar numbers and types of peptide and amino acid uptake systems as well as protein and carbohydrate secretion systems. The differences observed correlate with and may account, in part, for the different lifestyles of these 2 bacterial predators.
  • 2.

    【2hr】The Membrane Attack Complex/Perforin (MACPF) Superfamily

    包量

    机译 膜攻击复合物/穿孔素（MACPF）超家族
    摘要：The Membrane Attack Complex/Perforin (MACPF) superfamily consists of a diverse group of proteins involved in bacterial pathogenesis and sporulation as well as eukaryotic immunity, embryonic development, neural migration and fruiting body formation. The present work shows that the evolutionary relationships between the members of the superfamily, previously suggested by comparison of their tertiary structures, can also be supported by analyses of their primary structures. The superfamily includes the MACPF family (TC 1.C.39), the Cholesterol-dependent Cytolysin (CDC) family (TC 1.C.12.1 and 1.C.12.2) and the Pleurotolysin Pore-forming (Pleurotolysin B) family (TC 1.C.97.1), as revealed by expansion of each family by comparison against a large protein database, and by the comparisons of their Hidden Markov Models. Clustering analyses demonstrated grouping of the CDC homologues separately from the twelve MACPF subfamilies, which also grouped separately from the Pleurotolysin B family. Members of the MACPF superfamily revealed a remarkably diverse range of proteins spanning eukaryotic, bacterial and archaeal taxonomic domains, with notable variations in protein domain architectures. Our strategy should also be helpful in putting together other highly divergent protein families.
  • 3.

    【2hr】Synthetic switchable enzymes

    包量

    机译 合成可转换酶
    摘要：The construction of switchable, radiation-controlled, aptameric enzymes alias swenzymes is, in principle, feasible. We propose a strategy to make such catalysts from two (or more) aptamers each selected to bind specifically to one of the substrates in, for example, a two-substrate reaction. Construction of a combinatorial library of candidate swenzymes entails selecting a set of a million aptamers that bind one substrate and a second set of a million aptamers that bind the second substrate; the aptamers in these sets are then linked pairwise by a linker so bringing together the substrates. In the presence of the substrates, some linked aptamer pairs catalyze the reaction when exposed to external energy in the form of a specific frequency of low intensity, non-ionizing electromagnetic or acoustic radiation. Such swenzymes are detected via a separate, product-capturing, aptamer that changes conformation on capturing the product; this altered conformation allows it (1) to bind to every potential swenzyme in its vicinity (thereby giving a higher probability of capture to the swenzymes that generate the product) and (2) to bind to a sequence on a magnetic bead (thereby permitting purification of the swenzyme plus product-capturing aptamer by precipitation). Attempts to implement the swenzyme strategy may help elucidate fundamental problems in enzyme catalysis.
  • 4.

    【2hr】Control of Transposon-mediated Directed Mutation by the Escherichia coli Phosphoenolpyruvate:Sugar Phosphotransferase System

    包量

    机译 大肠杆菌磷酸烯醇丙酮酸：糖磷酸转移酶系统控制转座子介导的定向突变
    摘要：The phosphoenolpyruvate:sugar phosphotransferase system (PTS) has been shown to control transport, cell metabolism and gene expression. We here present results supporting the novel suggestion that in certain instances, it also regulates mutation rate. Directed mutations are defined as mutations that occur at higher frequencies when beneficial than when neutral or detrimental. To date, the occurrence of directed point mutations has not been documented and confirmed, but a few examples of transposon-mediated directed mutation have been reported. Here we focus on the first and best-studied example of directed mutation, which involves the regulation of Insertion Sequence-5 (IS5) hopping into a specific site upstream of the glpFK glycerol utilization operon in Escherichia coli. This insertional event specifically activates expression of the glpFK operon, allowing growth of wild type cells with glycerol as a carbon source in the presence of non-metabolizable glucose analogues which normally block glycerol utilization. The sugar transporting PTS controls this process by regulating levels of cytoplasmic glycerol-3-phosphate and cyclic AMP as established in previous publications. Direct involvement of the glycerol repressor, GlpR, and the cyclic AMP receptor protein, Crp, in the regulation of transposon-mediated directed mutation has been demonstrated.
  • 5.

    【2hr】Topological Predictions for Integral Membrane Channel and CarrierProteins

    包量

    机译 整体膜通道和载体的拓扑预测蛋白质类
    摘要：We evaluated topological predictions for nine different programs, HMMTOP, TMHMM, SVMTOP, DAS, SOSUI, TOPCONS, PHOBIUS, MEMSAT-SVM (hereinafter referred to as MEMSAT), and SPOCTOPUS. These programs were first evaluated using four large topologically well-defined families of secondary transporters, and the three best programs were further evaluated using topologically more diverse families of channels and carriers. In the initial studies, the order of accuracy was: SPOCTOPUS>MEMSAT>HMMTOP>TOPCONS>PHOBIUS>TMHMM>SVMTOP>DAS>S OSUI. Some families, such as the Sugar Porter family (2.A.1.1) of the Major Facilitator Superfamily (MFS; TC# 2.A.1) and the Amino acid/Polyamine/Organocation (APC) Family (TC# 2.A.3), were correctly predicted with high accuracy while others, such as the Mitochondrial Carrier (MC) (TC# 2.A.29) and the K+ transporter (Trk) families (TC# 2.A.38), were predicted with much lower accuracy. For small, topologically homogeneous families, SPOCTOPUS and MEMSAT were generally most reliable, while with large, more diverse superfamilies, HMMTOP often proved to have the greatest prediction accuracy. We next developed a novel program, TM-STATS, that tabulates HMMTOP, SPOCTOPUS or MEMSAT-based topologicalpredictions for any subdivision (class, subclass, superfamily, family,subfamily, or any combination of these) of the Transporter ClassificationDatabase (TCDB; ) and examined the following subclasses:α-type channel proteins (TC subclasses 1.A and 1.E), secretedporeforming toxins (TC subclass 1.C) and secondary carriers (subclass 2.A).Histograms 3 were generated for each of these subclasses, and the results wereanalyzed according to subclass, family and protein. The results provide anupdate of topological predictions for integral membrane transport proteins aswell as guides for the development of more reliable topological predictionprograms, taking family-specific characteristics into account.
  • 6.

    【2hr】Regulation of crp gene expression by the catabolite repressor/activator Cra in Escherichia coli

    包量

    机译 分解代谢阻遏物/激活物Cra对大肠杆菌中crp基因表达的调控
    摘要：Growth on several carbon sources is dependent on the catabolite repressor/activator (Cra) protein although a Cra consensus DNA binding site is not present in the control regions of the relevant catabolic operons. We show that Cra regulates growth by activating expression of the crp gene. It thereby mediates catabolite repression of catabolic operons by an indirect mechanism.
  • 7.

    【2hr】Gas vesicles across kingdoms: a comparative solid state NMR study

    包量

    机译 跨王国的气体囊泡：固态NMR对比研究
    摘要：The buoyancy organelles of aquatic microorganisms have to meet stringent specifications: allowing gases to equilibrate freely across the proteinaceous shell, preventing the condensation of water vapor inside the hollow cavity, and resisting collapse under hydrostatic pressures that vary with column depth. These properties are provided by the 7–8 kDa gas vesicle protein A (GvpA), repeats of which form all but small, specialized portions of the shell. Magic angle spinning NMR is uniquely capable of providing high resolution information on the fold and assembly of GvpA. Here we compare results for the gas vesicles of the haloarchae Halobacterium salinarum with those obtained previously for the cyanobacterium Anabaena flos-aquae. The data suggest that the two organisms follow similar strategies for avoiding water condensation. On the other hand, in its relatively shallow habitat, H. salinarum is able to avoid collapse with a less costly GvpA fold than is adopted by A. flos-aquae.
  • 8.

    【2hr】Microcompartments and Protein Machines in Prokaryotes

    包量

    机译 原核生物中的微区室和蛋白质机器
    • 作者：Milton H. Saier Jr.
    • 刊名：Journal of Molecular Microbiology and Biotechnology
    • -1年第0期
    摘要：The prokaryotic cell was once thought of as a “bag of enzymes” with little or no intracellular compartmentalization. In this view, most reactions essential for life occurred as a consequence of random molecular collisions involving substrates, cofactors and cytoplasmic enzymes. Our current conception of a prokaryote is far from this view. We now consider a bacterium or an archaeon as a highly structured, non-random collection of functional membrane-embedded and proteinaceous molecular machines, each of which serves a specialized function. In this article we shall present an overview of such microcompartments including (i) the bacterial cytoskeleton and the apparati allowing DNA segregation during cells division, (ii) energy transduction apparati involving light-driven proton pumping and ion gradient-driven ATP synthesis, (iii) prokaryotic motility and taxis machines that mediate cell movements in response to gradients of chemicals and physical forces, (iv) machines of protein folding, secretion and degradation, (v) metabolasomes carrying out specific chemical reactions, (vi) 24 hour clocks allowing bacteria to coordinate their metabolic activities with the daily solar cycle and (vii) proteinaceous membrane compartmentalized structures such as sulfur granules and gas vacuoles. Membrane-bounded prokaryotic organelles were considered in a recent JMMB written symposium concerned with membraneous compartmentalization in bacteria []. By contrast, in this symposium, we focus on proteinaceous microcompartments. These two symposia, taken together, provide the interested reader with an objective view of the remarkable complexity of what was once thought of as a simple non-compartmentalized cell.
  • 9.

    【2hr】Functional Advantages Conferred by Extracellular Prokaryotic Membrane Vesicles

    包量

    机译 细胞外原核膜囊泡赋予的功能优势
    摘要：The absence of subcellular organelles is a characteristic typically used to distinguish prokaryotic from eukaryotic cells. But recent discoveries do not support this dogma. Over the past 50 years, researchers have begun to appreciate and characterize Gram-negative bacterial outer membrane derived vesicles and Gram-positive and archaeal membrane vesicles. These extracellular, membrane-bound organelles can perform a variety of functions, including binding and delivery of DNA, transport of virulence factors, protection of the cell from outer membrane targeting antimicrobials, and ridding the cell of toxic envelope proteins. Here we review the contributions of these extracellular organelles to prokaryotic physiology and compare these with the contributions of the bacterial interior membrane bound organelles responsible for harvesting light energy and for generating magnetic crystals of heavy metals. Understanding the roles of these multifunctional extracellular vesicle organelles as microbial tools will help us to better realize the diverse interactions that occur in our polymicrobial world.
  • 10.

    【2hr】Simple Method to Differentiate among Rickettsia Species

    包量

    机译 区分立克次体种的简单方法
    摘要：In this work we present a new option to identify 11 rickettsial species that cause human rickettsioses, with some advantages over the previous methods described. Using rickettsial isolates from 11 Rickettsia species as a sample, we used the polymerase chain reaction to amplify a 990- to 1,000-bp DNA fragment from the ompB gene, common for the 11 Rickettsia species analyzed in this study, which were digested with AluI restriction enzyme to obtain different digestion patterns. This restriction pattern can be visualized using a polyacrylamide gel electrophoresis technique. Using this method we could differentiate between the 11 Rickettsia species analyzed regardless of the group to which the Rickettsia belonged. We developed a simple method to identify 11 Rickettsia species which cause human rickettsioses using polymerase chain reaction and restriction fragment length polymorphism techniques with the advantage that it only needs one amplicon and only one restriction enzyme to obtain the restriction pattern. The identification of the species infecting vectors, reservoirs, and humans is essential to establish the ecological and behavioral ecosystem involved in its maintenance and transmission in nature in the specific region where the pathogen is circulating. This method is very helpful to identify Rickettsia species in a short time.
  • 11.

    【2hr】Staphylococcus aureus persisters tolerant to bactericidal antibiotics

    包量

    机译 金黄色葡萄球菌对杀菌抗生素具有耐受力
    摘要：Bacterial persister cells are non- or slow growing reversible phenotypic variants of the wild type, tolerant to bactericidal antibiotics. We here analyzed Staphylococcus aureus persister levels by monitoring colony forming unit (CFU) counts of planktonically grown cells treated with six different antimicrobials over time. Model laboratory strains HG001-HG003, SA113 and small colony variant (SCV) strains hemB and menD were challenged by the compounds at different logs of minimal inhibitory concentration (MIC) in exponential or stationary growth phase. Antibiotic tolerance was usually elevated in SCV strains compared to normally growing cells and in stationary vs. exponential phase cultures. Biphasic killing kinetics, typical for persister cell enrichment, were observed in both growth phases under different selective conditions. Treatment of exponential phase cultures of HG001-HG003 with 10-fold MIC of tobramycin resulted in the isolation of persisters which upon cultivation on plates formed either normal or phenotypically stable small colonies. Trajectories of different killing curves indicated physiological heterogeneity within persister subpopulations. Daptomycin added at 100-fold MIC to stationary phase SA113 cells rapidly isolated very robust persisters. Fractions of antibiotic tolerant cells were observed with all S. aureus strains and mutants tested. Our results refute the hypothesis that S. aureus stationary phase cells are equivalent to persisters, as not all of these cells showed antibiotic tolerance. Isolation of S. aureus persisters of different robustness seems to dependent on the kind and concentration of the antibiotic, as well as on the strain used.
  • 12.

    【2hr】Stress-Induced Modulators of Repeat Instability and Genome Evolution

    包量

    机译 重复诱导不稳定性和基因组进化的应激诱导调节剂
    摘要：Evolution hinges on the ability of organisms to adapt to their environment. A key regulator of adaptability is mutation rate, which must be balanced to maintain genome fidelity while permitting sufficient plasticity to cope with environmental changes. Multiple mechanisms govern an organism's mutation rate. Constitutive mechanisms include mutator alleles that drive global, permanent increases in mutation rates, but these changes are confined to the subpopulation that carries the mutator allele. Other mechanisms focus mutagenesis in time and space to improve the chances that adaptive mutations can spread through the population. For example, environmental stress can induce mechanisms that transiently relax the fidelity of DNA repair to bring about a temporary increase in mutation rates during times when an organism experiences a reduced fitness for its surroundings, as has been demonstrated for double-strand break repair in Escherichia coli. Still, other mechanisms control the spatial distribution of mutations by directing changes to especially mutable sequences in the genome. In eukaryotic cells, for example, the stress-sensitive chaperone Hsp90 can regulate the length of trinucleotide repeats to fine-tune gene function and can regulate the mobility of transposable elements to enable larger functional changes. Here, we review the regulation of mutation rate, with special emphasis on the roles of tandem repeats and environmental stress in genome evolution.
  • 13.

    【2hr】What Limits the Efficiency of Double-Strand Break-Dependent Stress-Induced Mutation in Escherichia coli?

    包量

    机译 是什么限制了大肠杆菌中双链断裂依赖性应激诱导突变的效率？
    摘要：Stress-induced mutation is a collection of molecular mechanisms in bacterial, yeast and human cells that promote mutagenesis specifically when cells are maladapted to their environment, i.e. when they are stressed. Here, we review one molecular mechanism: double-strand break (DSB)-dependent stress-induced mutagenesis described in starving Escherichia coli. In it, the otherwise high-fidelity process of DSB repair by homologous recombination is switched to an error-prone mode under the control of the RpoS general stress response, which licenses the use of error-prone DNA polymerase, DinB, in DSB repair. This mechanism requires DSB repair proteins, RpoS, the SOS response and DinB. This pathway underlies half of spontaneous chromosomal frameshift and base substitution mutations in starving E. coli [Proc Natl Acad Sci USA 2011;108:13659–13664], yet appeared less efficient in chromosomal than F′ plasmid-borne genes. Here, we demonstrate and quantify DSB-dependent stress-induced reversion of a chromosomal lac allele with DSBs supplied by I-SceI double-strand endonuclease. I-SceI-induced reversion of this allele was previously studied in an F′. We compare the efficiencies of mutagenesis in the two locations. When we account for contributions of an F′-borne extra dinB gene, strain background differences, and bypass considerations of rates of spontaneous DNA breakage by providing I-SceI cuts, the chromosome is still ∼100 times less active than F. We suggest that availability of a homologous partner molecule for recombinational break repair may be limiting. That partner could be a duplicated chromosomal segment or sister chromosome.
  • 14.

    【2hr】Functional Analysis of the p40 and p75 Proteins from Lactobacillus casei BL23

    包量

    机译 干酪乳杆菌BL23 p40和p75蛋白的功能分析
    摘要：The genomes of Lactobacillus casei/paracasei and Lactobacillus rhamnosus strains carry two genes encoding homologues of p40 and p75 from L. rhamnosus GG, two secreted proteins which display anti-apoptotic and cell protective effects on human intestinal epithelial cells. p40 and p75 carry cysteine, histidine-dependent aminohydrolase/peptidase (CHAP) and NLPC/P60 domains, respectively, which are characteristic of proteins with cell-wall hydrolase activity. In L. casei BL23 both proteins were secreted to the growth medium and were also located at the bacterial cell surface. The genes coding for both proteins were inactivated in this strain. Inactivation of LCABL_00230 (encoding p40) did not result in a significant difference in phenotype, whereas a mutation in LCABL_02770 (encoding p75) produced cells that formed very long chains. Purified glutathione-S-transferase (GST)-p40 and -p75 fusion proteins were able to hydrolyze the muropeptides from L. casei cell walls. Both fusions bound to mucin, collagen and to intestinal epithelial cells and, similar to L. rhamnosus GG p40, stimulated epidermal growth factor receptor phosphorylation in mouse intestine ex vivo. These results indicate that extracellular proteins belonging to the machinery of cell-wall metabolism in the closely related L. casei/paracasei-L. rhamnosus group are most likely involved in the probiotic effects described for these bacteria
  • 15.

    【2hr】An Escherichia coli-Based Cell-Free System for Large-Scale Production of Functional Mammalian Membrane Proteins Suitable for X-Ray Crystallography

    包量

    机译 基于大肠杆菌的无细胞系统用于大规模生产适用于X射线晶体学的功能性哺乳动物膜蛋白
    摘要：A cell-free expression system using an Escherichia coli extract was adapted for large-scale expression and purification of mammalian membrane proteins. The system was tested with a set of human membrane proteins of different sizes, numbers of transmembrane domains, oligomeric arrangements, and native membrane locations. Tens of milligrams of protein were readily expressed and purified from an overnight cell-free reaction. Both reaction ‘mode A’ (proteins were expressed as precipitant) and ‘mode B’ (proteins were expressed in the presence of mild detergents to keep them soluble) were investigated. The combination of ‘mode B’ and the right detergents, used in the subsequent extraction and purification steps, is critical for obtaining properly folded proteins (CX32 and VDAC1) that can be crystallized and diffracted (VDAC1). The E. coli cell-free system is capable of efficient expression of many mammalian membrane proteins. However, fine-tuning of the system, especially to facilitate proper protein folding, will be required for each specific target.
  • 16.

    【2hr】A specialized version of the HD hydrolase domain implicated in signal transduction

    包量

    机译 HD水解酶结构域的专门版本涉及信号转导
    摘要：
  • 17.

    【2hr】Science Innovation and the Future of Humanity

    包量

    机译 科学创新与人类的未来
    摘要：
  • 18.

    【2hr】Analysis of 58 families of Holins Using A Novel Program PhyST

    包量

    机译 使用新型程序PhyST分析58个霍林家族
    摘要：We have designed a freely accessible program, PhyST, that allows the automated characterization of any family of homologous proteins within the Transporter Classification Database (TCDB). The program performs an NCBI-PSI-BLAST search and reports (1) the average protein sequence length ± standard deviations (SD), (2) average predicted number of transmembrane segments (TMSs), (3) total number of homologues retrieved, (4) a quantitative list of all source phyla and (5) potential fusion proteins of sizes considerably exceeding the average size of the proteins retrieved. We have applied this program to 58 families of holins, and the results are presented. The results show that holins are very rarely fused to other protein domains, suggesting that holins form transmembrane pores as homoooligomers without the participation of other proteins or protein domains.
  • 19.

    【2hr】The Bacterial Phosphotransferase System: New frontiers 50 years after its discovery

    包量

    机译 细菌磷酸转移酶系统：发现后50年的新领域
    • 作者：Milton H. Saier Jr
    • 刊名：Journal of Molecular Microbiology and Biotechnology
    • -1年第0期
    摘要：
  • 20.

    【2hr】Synthesis and Physicochemical Characterization of D-Tagatose-1-phosphate: The Substrate of the Tagatose-1-Phosphate Kinase TagK in the PTS-mediated D-Tagatose Catabolic Pathway of Bacillus licheniformis

    包量

    机译 D-塔格糖-1磷酸的合成及理化特性：地衣芽孢杆菌PTS介导的D-塔格糖分解代谢途径中塔格糖-1-磷酸激酶TagK的底物。
    摘要：We report the first enzymatic synthesis of D-tagatose-1-phosphate (Tag-1P) by the multi-component PEP-dependent:tag-PTS present in tagatose-grown cells of Klebsiella pneumoniae. Physicochemical characterization by 31P and 1H NMR spectroscopy reveals that, in solution, this derivative is primarily in the pyranose form. Tag-1P was used to characterize the putative tagatose-1-phosphate kinase (TagK) of the >Bacillus >licheniformis PTS-mediated D->Tagatose catabolic >Pathway (>Bli-TagP). For this purpose, a soluble protein fusion was obtained with the 6 His-tagged trigger factor (TFHis6) of Escherichia coli. The active fusion enzyme was named TagK-TFHis6. Tag-1P and D-fructose-1-phosphate (Fru-1P) are substrates for the TagK-TFHis6 enzyme, whereas the isomeric derivatives D-tagatose-6-phosphate (Tag-6P) and D-fructose-6-phosphate (Fru-6P) are inhibitors. Studies of catalytic efficiency (kcat/Km) reveal that the enzyme specificity is markedly in favor of Tag-1P as substrate. Importantly, we show in vivo that the transfer of the phosphate moiety from PEP to the B. licheniformis tagatose-specific enzyme II (EIITag) in E.coli is inefficient. The capability of the PTS general cytoplasmic components of B. subtilis, HPr and EI, to restore the phosphate transfer is demonstrated.
题名 作者 来源 发表时间

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号