bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron transport to periplasmic nitrate reductase (NapA) of Wolinella succinogenes is independent of a NapC protein
Authors: Simon Jörg , Sänger Monica , Schuster Stephan C. , Gross Roland 
Published: June 2003

SummaryThe rumen bacterium Wolinella succinogenes grows by respiratory nitrate ammonification with formate as electron donor. Whereas the enzymology and coupling mechanism of nitrite respiration is well known, nitrate reduction to nitrite has not yet been examined. We report here that intact cells and cell fractions catalyse nitrate and chlorate reduction by reduced viologen dyes with high specific activities. A gene cluster encoding components of a putative periplasmic nitrate reductase system (napA, G, H, B, F, L, D) was sequenced. The napA gene was inactivated by inserting a kanamycin resistance gene cassette. The resulting mutant did not grow by nitrate respiration and did not reduce nitrate during growth by fumarate respiration, in contrast to the wild type. An antigen was detected in wild‐type cells using an antiserum raised against the periplasmic nitrate reductase (NapA) from Paracoccus pantotrophus. This antigen was absent in the W. succinogenes napA mutant. It is concluded that the periplasmic nitrate reductase NapA is the only respiratory nitrate reductase in W. succinogenes, although a second nitrate‐reducing enzyme is apparently induced in the napA mutant. The nap cluster of W. succinogenes lacks a napC gene whose product is thought to function in quinol oxidation and electron transfer to NapA in other bacteria. The W. succinogenes genome encodes two members of the NapC/NirT family, NrfH and FccC. Characterization of corresponding deletion mutants indicates that neither of these two proteins is required for nitrate respiration. A mutant lacking the genes encoding respiratory nitrite reductase (nrfHA) had wild‐type properties with respect to nitrate respiration. A model of the electron transport chain of nitrate respiration is proposed in which one or more of the napF, G, H and L gene products mediate electron transport from menaquinol to the periplasmic NapAB complex. Inspection of the W. succinogenes genome sequence suggests that ammonia formation from nitrate is catalysed exclusively by periplasmic respiratory enzymes.
Secretion of a soluble colonization factor by the TCP type 4 pilus biogenesis pathway in Vibrio cholerae
Authors: Kirn Thomas J. , Bose Niranjan , Taylor Ronald K. 
Published: June 2003

SummaryColonization of the human small intestine by Vibrio cholerae requires the type 4 toxin co‐regulated pilus (TCP). Genes encoding the structure and biogenesis functions of TCP are organized within an operon located on the Vibrio Pathogenicity Island (VPI). In an effort to elucidate the functions of proteins involved in TCP biogenesis, in frame deletions of all of the genes within the tcp operon coding for putative pilus biogenesis proteins have been constructed and the resulting mutants characterized with respect to the assembly and function of TCP. As a result of this analysis, we have identified the product of one of these genes, tcpF, as a novel secreted colonization factor. Chromosomal deletion of tcpF yields a mutant that retains in vitro phenotypes associated with the assembly of functional TCP yet is severely attenuated for colonization of the infant mouse intestine. Furthermore, we have determined that the mechanism by which TcpF is translocated across the bacterial outer membrane requires the TCP biogenesis machinery and is independent of the type II extracellular protein secretion (EPS) system. These results suggest a dual role for the TCP biogenesis apparatus in V. cholerae pathogenesis and a novel mechanism of intestinal colonization mediated by a soluble factor.
Control of rpoS transcription in Escherichia coli and Pseudomonas: why so different?
Authors: Venturi Vittorio 
Published: June 2003

SummaryIn Escherichia coli, the stationary phase alternative sigma factor σs controls the expression of genes involved cell survival in response to cessation of growth (stationary phase) and provides cross‐protection to various stresses. Levels of σs increase dramatically at the onset of stationary phase and are regulated at the transcriptional, post‐transcriptional and post‐translational level, making this one of the most complex regulatory systems in bacteria. The basic mechanisms for the control of translation and σs proteolysis have been understood. However, studies on the transcriptional control in E. coli lag behind and are controversial. The cAMP‐CRP complex and the two component BarA/UvrY system have been implicated and, ppGpp and polyphosphate appear to have a signalling role. σs has also been reported to be a general stress regulator in the fluorescent pseudomonads (Pseudomonas aeruginosa, P. fluorescens and P. putida) and recent studies on σs regulation highlight that transcriptional regulation in these bacteria apparently plays a major role. Global regulatory systems, the GacA/GacS two component system and quorum sensing all affect rpoS expression, as does the TetR family PsrA regulator that directly binds to‐ and activates the rpoS promoter in stationary phase. This striking difference in regulation between E. coli and Pseudomonas can be partly attributed to the differences in the functional role of σs in the two bacterial species. This report will review mainly recent studies on rpoS transcriptional regulation and will try to rationalize the current knowledge into a working model.
Characterization of two alternative promoters for integrase expression in the clc genomic island of Pseudomonas sp. strain B13
Authors: Sentchilo V. , Zehnder A. J. B. , Van Der Meer J. R. 
Published: June 2003

SummaryThe clc genomic island is a 105 kb integrative and conjugative element (ICE) in Pseudomonas sp. strain B13, which encodes metabolism of 3‐chlorocatechol. The clc island is integrated in a tRNAGly gene, but can excise and form a circular intermediate in which both ends are connected. The integrase gene (intB13) of the clc genomic island is located at the right end, 202 bp from the junction site facing inwards. Fragments upstream of intB13 in the circular form and in the integrated form were fused to a promoterless gfp gene for Green Fluorescent Protein and introduced in monocopy onto the chromosome of strain B13. Quantitative GFP fluorescence measurements in individual cells of the different B13‐derivatives revealed that the circular form fragment contained a strong constitutive promoter (Pcirc) driving intB13 expression in all cells. By using primer extension Pcirc could be mapped near the left end of the clc element and Pcirc can therefore only control intB13 expression when left and right ends are connected as in the circular form. Expression from intB13 upstream fragments from the integrated clc element was weaker than that from Pcirc and only occurred in maximally 15% of individual cells in a culture. A promoter (Pint) could be roughly mapped in this region by using reverse‐transcription PCR and by successively shortening the fragment from the 5′ end. Transposon mutants in cloned left end sequences of the clc element were selected which had lost the activation potential on the Pint promoter and those which resulted in overexpression of GFP from Pint. The DNA sequence of the region of the transposon insertions pointed to a relatively well conserved area among various other genomic islands. The activator mutants mapped in an open reading frame (ORF) encoding a 175 amino acid protein without any significant similarity to functionally characterized proteins in the databases.
A novel sheathed surface organelle of the Helicobacter pylori cag type IV secretion system
Authors: Rohde Manfred , Püls Jürgen , Buhrdorf Renate , Fischer Wolfgang , Haas Rainer 
Published: June 2003

SummaryType I strains of Helicobacter pylori (Hp) use a type IV secretion system (T4SS), encoded by the cag pathogenicity island (cag‐PAI), to deliver the bacterial protein CagA into eukaryotic cells and to induce interleukin‐8 secretion. Translocated CagA is activated by tyrosine phosphorylation involving Src‐family kinases. The mechanism and structural basis for type IV protein secretion is not well understood. We describe here, by confocal laser scanning microscopy and field emission scanning electron microscopy, a novel filamentous surface organelle which is part of the Hp T4SS. The organelle is often located at one bacterial pole but can be induced by cell contact also along the lateral side of the bacteria. It consists of a rigid needle, covered focally or completely by HP0527 (Cag7 or CagY), a VirB10‐homologous protein. HP0527 is also clustered in the outer membrane. The VirB7‐homologous protein HP0532 is found at the base of this organelle. These observations demonstrate for the first time by microscopic techniques a complex T4SS‐associated, sheathed surface organelle reminiscent to the needle structures of bacterial type III secretion systems.
Transgenic mice expressing the diphtheria toxin receptor are sensitive to the toxin
Authors: Cha Jeong‐Heon , Chang Mee Young , Richardson James A. , Eidels Leon 
Published: June 2003

SummaryWhereas diphtheria and the mechanism of action of diphtheria toxin, the bacterial molecule that induces the disease, have been studied and understood for some time, the receptor that allows animal cells to bind the toxin escaped identification until recently. The receptor was identified by its ability to confer toxin‐sensitivity to mouse cells, which are normally toxin‐resistant. Although mice are also naturally resistant, we now demonstrate that transgenic mice expressing the diphtheria toxin receptor are as sensitive to the toxin as are humans and other toxin‐sensitive animals. These transgenic mice provide a suitable model for studying modern antidotes for diphtheria.
Interaction between the IncHI1 plasmid R27 coupling protein and type IV secretion system: TraG associates with the coiled‐coil mating pair formation protein TrhB
Authors: Gilmour Matthew W. , Gunton James E. , Lawley Trevor D. , Taylor Diane E. 
Published: June 2003

SummaryAssemblies of plasmid‐encoded proteins direct the conjugative transfer of plasmid DNA molecules between bacteria. These include the membrane‐associated mating pair formation (Mpf) complex necessary for pilus production and the cytoplasmic relaxosome required for DNA processing. The proposed link between these distinct protein complexes is the coupling protein (the TraG family of proteins). Interactions between the coupling protein and relaxosome components have been previously characterized and we document here, for the first time, a direct interaction between the coupling protein and an Mpf protein. Using the adenylate cyclase bacterial two‐hybrid (BTH) system, we present in vivo evidence that the IncHI1 plasmid R27‐encoded proteins TraG and TrhB interact. This interaction was verified through a co‐immunoprecipitation reaction. We have also been able to delineate the interaction domain of TrhB to TraG by showing a positive interaction using the first 220 amino acids of TrhB (452 aa). TrhB has a proline‐rich domain from amino acids 135–173 which may serve to facilitate protein interactions and/or periplasmic extension. TrhB self association was detected using far‐Western, co‐immunoprecipitation, and also BTH analysis, which was used to define the homotypic interaction domain, comprising a predicted coiled‐coil region at residues 77–124 of TrhB. These data support a model in which the coupling protein interacts with an Mpf component to target the transferring DNA strand held by the relaxosome to the transmembrane Mpf complex.
A binuclear zinc transcription factor binds the host isoflavonoid‐responsive element in a fungal cytochrome p450 gene responsible for detoxification
Authors: Khan Rana , Tan Reynold , Mariscal Amanda Galvez , Straney David 
Published: June 2003

SummaryThe PDA1 gene of the filamentous fungus Nectria haematococca MPVI (anamorph: Fusarium solani) encodes pisatin demethylase, a cytochrome P450. Pisatin is a fungistatic isoflavonoid produced by garden pea (Pisum sativum), a host for this fungus. Pisatin demethylase detoxifies pisatin and functions as a virulence factor for this fungus. Pisatin induces PDA1 expression both in cultured mycelia as well as during pathogenesis on pea. The regulatory element within PDA1 that provides pisatin‐responsive expression was identified using a combination of in vivo functional analysis and in vitro binding analysis. The 40 bp pisatin‐responsive element is located 635 bp upstream of the PDA1 transcription start site. This element was sufficient to provide strong pisatin‐induced expression to a minimal promoter in vivo and was required for pisatin regulation of the PDA1 promoter. A gene encoding a DNA‐binding protein specific to this 40 bp element was isolated from a N. haematococca cDNA library using the yeast one‐hybrid screen. The cloned gene possesses sequence motifs found in the binuclear zinc (Cys 6‐Zn 2) family of transcription factors unique to fungi. The results suggest that it is a regulator of this fungal cytochrome P450 gene and may provide pisatin‐responsive regulation.
Glycerol dehydrogenase, encoded by gldB is essential for osmotolerance in Aspergillus nidulans
Authors: De Vries Ronald P. , Flitter Simon J. , Van De Vondervoort Peter J. I. , Chaveroche Marie‐Kim , Fontaine Thierry , Fillinger Sabine , Ruijter George J. G. , D’Enfert Christophe , Visser Jaap 
Published: June 2003

SummaryWe have characterized the Aspergillus nidulans gldB gene encoding a NADP+‐dependent glycerol dehydrogenase. A basal expression level was observed for gldB, which increased significantly under conditions of hyper‐osmotic shock (1 M NaCl). Growth of strains in which gldB was disrupted was severely reduced on plates containing 1% glucose and 1 M NaCl, but these strains were able to grow on plates containing 1 M NaCl and 1% glycerol, arabitol, mannitol or erythritol. Uptake of these polyols compensated for the inability of the gldB disruptants to produce glycerol. Presence of 1% glucose in these plates prevented growth restoration by all the polyols tested with the exemption of glycerol, indicating that uptake of mannitol, arabitol and erythritol is subject to glucose repression, whereas uptake of glycerol is significantly less or not repressed. No intracellular glycerol dehydrogenase activity could be detected in the gldB disruption strains. Intracellular glycerol levels in these strains were strongly decreased compared to wild type, whereas intracellular mannitol, erythritol and arabitol levels were increased. Conidia of the gldB disruption strain did not accumulate glycerol upon germination in glucose media with or without 1 M NaCl and germ tube emergence was significantly delayed in this strain in the presence of 1 M NaCl in comparison to the wild type. These data indicate that gldB is essential for osmotolerance in A. nidulans and that the pathways for glycerol biosynthesis under osmotic stress differ between yeast and filamentous fungi.
The extracellular proteome of Bacillus subtilis under secretion stress conditions
Authors: Antelmann Haike , Darmon Elise , Noone David , Veening Jan‐Willem , Westers Helga , Bron Sierd , Kuipers Oscar P. , Devine Kevin M. , Hecker Michael , Van Dijl Jan Maarten 
Published: June 2003

SummaryThe accumulation of malfolded proteins in the cell envelope of the Gram‐positive eubacterium Bacillus subtilis was previously shown to provoke a so‐called secretion stress response. In the present studies, proteomic approaches were employed to identify changes in the extracellular proteome of B. subtilis in response to secretion stress. The data shows that, irrespective of the way in which secretion stress is imposed on the cells, the levels of only two extracellular proteins, HtrA and YqxI, display major variations in a parallel manner. Whereas the extracellular level of the HtrA protease is determined through transcriptional regulation, the level of YqxI in the growth medium is determined post‐transcriptionally in an HtrA‐dependent manner. In the absence of secretion stress, the extracellular levels of HtrA and YqxI are low because of extracytoplasmic proteolysis. Finally, the protease active site of HtrA is dispensable for post‐transcriptional YqxI regulation. It is known that Escherichia coli HtrA has combined protease and chaperone‐like activities. As this protein shares a high degree of similarity with B. subtilis HtrA, it can be hypothesized that both activities are conserved in B. subtilis HtrA. Thus, a chaperone‐like activity of B. subtilis HtrA could be involved in the appearance of YqxI on the extracellular proteome.
Identification of additional TnrA‐regulated genes of Bacillus subtilis associated with a TnrA box
Authors: Yoshida Ken‐ichi , Yamaguchi Hirotake , Kinehara Masaki , Ohki Yo‐hei , Nakaura Yoshiko , Fujita Yasutaro 
Published: June 2003

Summary Bacillus subtilis TnrA is a global regulator that responds to the availability of nitrogen sources and both activates and represses many genes during nitrogen‐limited growth. In order to obtain a holistic view of the gene regulation depending on TnrA, we performed a genome‐wide screening for TnrA‐regulated genes associated with a TnrA box. A combination of DNA microarray hybridization and a genome‐wide search for TnrA boxes allowed us to find 36 TnrA‐regulated transcription units associated with a putative TnrA box. Gel retardation assaying, using probes carrying at least one putative TnrA box and the deletion derivatives of each box, indicated that 17 out of 36 transcription units were likely TnrA targets associated with the TnrA boxes, two of which (nasA and nasBCDEF) possessed a common TnrA box. The sequences of these TnrA boxes contained a consensus one, TGTNANAWWWTMTNACA. The TnrA targets detected in this study were nrgAB, pucJKLM, glnQHMP, nasDEF, oppABCDF, nasA, nasBCDEF and ywrD for positive regulation, and gltAB, pel, ywdIJK, yycCB, yttA, yxkC, ywlFG, yodF and alsT for negative regulation, nrgAB and gltAB being well‐studied TnrA targets. It was unexpected that the negatively regulated TnrA targets were as many as the positively regulated targets. The physiological role of the TnrA regulon is discussed.
A mutation in the membrane subunit of an ABC transporter LolCDE complex causing outer membrane localization of lipoproteins against their inner membrane‐specific signals
Authors: Narita Shin‐ichiro , Kanamaru Kyoko , Matsuyama Shin‐ichi , Tokuda Hajime 
Published: June 2003

SummaryLipoproteins in Gram‐negative bacteria are anchored to the inner or outer membrane via fatty acids attached to the N‐terminal cysteine. The residue at position 2 determines the membrane specificity. An ATP binding cassette transporter LolCDE complex releases lipoproteins with residues other than aspartate at position 2 from the inner membrane, whereas those with aspartate at position 2 are rejected by LolCDE and therefore remain in the inner membrane. For further understanding of this rejection mechanism, a novel strategy was developed to select mutants in which lipoproteins with aspartate at position 2 are released. The isolated mutants carried an alanine to proline mutation at position 40 of LolC, a membrane subunit of the LolCDE complex. A significant portion of an inner membrane lipoprotein, L10P(DQ), was localized to the outer membrane when the LolC mutant was expressed. Periplasmic chaperone LolA formed a complex with the released L10P(DQ), which was subsequently incorporated into the outer membrane in a LolB‐dependent manner, indicating that neither LolA nor LolB rejects lipoproteins with aspartate at position 2. The amount of the LolC mutant co‐purified with LolD and LolE after membrane solubilization was reduced significantly. Taken together, these results indicate that the mutation causes destabilization of the LolCDE complex and concomitantly prevents the accurate recognition of lipoprotein‐sorting signals.
Selective upregulation of a single distinctly structured var gene in chondroitin sulphate A‐adhering Plasmodium falciparum involved in pregnancy‐associated malaria
Authors: Salanti Ali , Staalsoe Trine , Lavstsen Thomas , Jensen Anja T. R. , Sowa M. P. Kordai , Arnot David E. , Hviid Lars , Theander Thor G. 
Published: June 2003

SummaryCytoadhesion of infected red blood cells (iRBC) is mediated through parasite‐encoded, clonally variant surface antigens (VSA) and is a central process in the pathogenesis of Plasmodium falciparum malaria. Pregnancy‐associated malaria (PAM) has been linked to VSA‐mediated adhesion of iRBC to the glycosaminoglycan chondroitin sulphate A (CSA) in the placental intervillous space. Several studies have pointed to members of the PfEMP1 VSA family as mediators of CSA‐specific iRBC sequestration in the placenta. Here, we report marked upregulation of a single var gene in several P. falciparum parasite isolates after selection for adhesion to CSA in vitro. The gene belongs to a highly conserved and common var gene subfamily (var2csa). The var2csa genes are structurally distinct from all other var genes in the parasite genome in lacking both CIDR and DBL‐γ domains. These domains have previously been implicated in PfEMP1‐mediated adhesion to CD36 and CSA. We also show that var2csa was transcribed at higher levels in three placental parasite isolates compared with transcription in parasites from peripheral blood of two children with P. falciparum malaria. This var gene thus has the properties expected of a gene encoding the parasite adhesion molecule that initiates the pathology associated with PAM.
Species specificity in the activation of Xer recombination at dif by FtsK
Authors: Yates James , Aroyo Mira , Sherratt David J. , Barre François‐Xavier 
Published: June 2003

SummaryIn Escherichia coli, chromosome dimers are resolved to monomers by the addition of a single cross‐over at a specific locus on the chromosome, dif. Recombination is performed by two tyrosine recombinases, XerC and XerD, and requires the action of an additional protein, FtsK. We show that Haemophilus influenzae FtsK activates recombination by H. influenzae XerCD at H. influenzae dif. However, it cannot activate recombination by E. coli XerCD. Reciprocally, E. coli FtsK cannot activate recombination by the H. influenzae recombinases at H. influenzae dif. We took advantage of this species specificity to gain further insight into the mechanism of activation of Xer recombination at dif by FtsK. We mapped the region of FtsK implicated in species specificity to the extreme 140‐amino‐acid C‐terminal residues of the protein. Our results suggest that FtsK interacts directly with XerCD in order to activate recombination at dif.