bluuebunny/crossref_metadata_2025_split huggingface dataset:
Translocation of precytochrome C2 into intracytoplasmic membrane vesicles of Rhodobacter capsulatus requires a peripheral membrane protein
Authors: Wieseler Beate , Müller Matthias 
Published: October 2006

Summary Rhodobacter capsulatus is a member of the group α‐purple bacteria which are closely related to the ancestral endosymbiont that gave rise to mitochondria. It has therefore been hypothesized that the molecular mechanisms governing protein export in α‐purple bacteria have been conserved during the evolution of mitochondria. To enable analysis of protein export in α‐purple bacteria we describe here the development of a homologous cell‐free synthesis/export system consisting entirely of components of R. capsulatus. Translocation of precytochrome C2 into intracytoplasmic membrane vesicles of this organism was found to require the proton‐motive force and proceed at a significantly higher efficiency when membranes were present during protein synthesis. Furthermore, we show that, in this cell‐free system, translocation depends on a preparation of peripheral membrane proteins Which do not possess detectable SecA‐ and SecB‐like actvities.
Isolation of a prokaryotic metallothionein locus and analysis of transcriptional control by trace metal ions
Authors: Huckle James W. , Morby Andrew P. , Turner Jennifer S. , Robinson Nigel J. 
Published: October 2006

SummaryIn eukaryotes, metallothioneins (MTs) are involved in cellular responses to elevated concentrations of certain metal ions. We report the isolation and analysis of a prokaryotic MT locus from Synechococcus PCC 7942. The MT locus (smt) includes smtA, which encodes a class II MT, and a divergently transcribed gene, smtB. The sites of transcription initiation of both genes have been mapped and features within the smt operator‐promoter region identified. Elevated concentrations of the ionic species of Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn elicited an increase in the abundance of smtA transcripts. There was no detectable effect of elevated metal (Cd) on smtA transcript stability. Sequences upstream of smtA, fused to a promoterless lacZ gene, conferred metal‐dependent β‐galactosidase activity in Synechococcus PCC 7942 (strain R2‐PIM8). At maximum permissive concentrations, Zn was the most potent elicitor in vivo, followed by Cu and Cd with slight induction by Co and Ni. The deduced SmtB polypeptide has similarity to the ArsR and CadC proteins involved in resistance to arsenate/arsenite/antimonite and to Cd, contains a predicted helix‐turn‐helix DNA‐binding motif and is shown to be a repressor of transcription from the smtA operator‐promoter.
Deletion within the metallothionein locus of cadmium‐tolerant Synechococcus PCC 6301 involving a highly iterated palindrome (HIP1)
Authors: Gupta Amit , Morby Andrew P. , Turner Jennifer S. , Whitton Brian A. , Robinson Nigel J. 
Published: October 2006

SummaryGenomic rearrangements involving amplification of metallothionein (MT) genes have been reported in metal‐tolerant eukaryotes. Similarly, we have recently observed amplification and rearrangement of a prokaryotic MT locus, smt, in cells of Synechococcus PCC 6301 selected for Cd tolerance. Following the characterization of this locus, the altered smt region has now been isolated from a Cd‐tolerant cell line, C3.2, and its nucleotide sequence determined. This has identified a deletion within smtB, which encodes a trans‐acting repressor of smt transcription. Two identical palindromic octanucleotides (5′‐GCGATC‐GC‐3′) traverse both borders of the excised element. This palindromic sequence is highly represented in the smt locus (7 occurrences in 1326 nucleotides) and analysis of the GenBank/EMBL /DDB J DNA Nucleotide Sequence Data Libraries reveals that this is a highly iterated palindrome (HIP1) in other known sequences from Synechococcus strains (estimated to occur at an average frequency of once every c. 664 bp). HIP1 is also abundant in the genomes of other cyanobacteria. The functional significance of smtB deletion and the possible role of HIP1 in genome plasticity and adaptation in cyanobacteria are discussed.
Genetic analysis of the φC31 ‐specific phage growth limitation (Pgl) system of Streptomyces coelicolor A3(2)
Authors: Laity Carole , Chater Keith F. , Lewis Cinzia G. , Buttner Mark J. 
Published: October 2006

SummaryThe phage growth limitation (Pgl) system of Streptomyces coelicolor A3(2) was shown to be specific to φC31 homo‐immune phages, and to be absent from the closely related strain Streptomyces Iividans. A 16 kb fragment of S. coelicolor A3(2) DNA was isolated which complemented the Pgl− phenotype of J1501, a pgl mutant derivative of the PgltsS. coelicolor strain M130. The cloned DNA complemented only half of the available pgl mutants, which therefore represented at least two groups, designated Pgl class A and class B strains. It follows that more than one kind of high‐frequency genetic event can lead to the Pgl− phenotype. Crosses between class A and class B strains yielded high frequencies of Pgl+ recombinants. Crosses between strains of the same class gave no Pgl+ recombinants. The cloned DNA was altered by deletion or apparent point mutation upon passage through the two class B strains tested, such that it was no longer capable of complementing class A strains. This accumulation of mutations might suggest that the expression of the cloned DNA is toxic to at least some class B strains. The nature of the genetic instability associated with the Pgl system was not detectable by Southern blot analysis.
Transition‐state regulators: sentinels of Bacillus subtilis post‐exponential gene expression
Authors: Strauch Mark A. , Hoch James A. 
Published: October 2006

SummaryWhen Bacillus subtilis encounters a nutrient‐depleted environment, it expresses a wide variety of genes that encode functions in alternative pathways of metabolism and energy production. Expression of these genes first occurs during the transition from active growth into stationary phase and is controlled by a class of proteins termed transition‐state regulators. In several instances, a given gene is redundantly controlled by two or more of these regulators and many of these regulators control genes in numerous different pathways. The AbrB, Hpr and Sin proteins are the best‐studied examples of these regulatory molecules. Their role is to prevent inappropriate and possibly detrimental functions from being expressed during exponential growth when they are not needed. They serve as elements integrating sporulation with ancillary stationary‐phase phenomena and appear to participate in the timing of early sporulation events and in fine‐tuning the magnitude of gene expression in response to specific environmental conditions.
Protein HU binds specifically to kinked DNA
Authors: Pontiggia Andrea , Negri Armando , Beltrame Monica , Bianchi Marco E. 
Published: October 2006

SummaryWe have purified the main four‐way junction DNA‐binding protein of Escherichia coli, and have found It to be the well‐known HU protein. HU protein recognizes with high‐affinity one of the angles present in the junction, a molecule with the shape of an X. Other DNA structures characterized by sharp bends or kinks, like bulged duplex DNAs containing unpaired bases, are also bound. HU protein appears to inhibit cruciform extrusion from supercoiled inverted repeat (palindromic) DNA, either by constraining supercoiling or by trapping a metastable interconversion intermediate. All these properties are analogous to the properties of the mammalian chromatin protein HMG1. We suggest that HU is a prokaryotic HMG1‐like protein rather than a histone‐like protein.
Isolation of dnaJ, dnaK, and grpE homologues from Borrelia burgdorferi and complementation of Escherichia coli mutants
Authors: Tilly Kit , Hauser Robyn , Campbell Jim , Ostheimer Gerard J. 
Published: October 2006

SummaryThe heat‐shock proteins DnaJ, DnaK, and GrpE are involved in the replication of various species of DNA in Escherichia coli, in addition to their roles in other processes, including protein disaggregation and export. We have cloned the Borrelia burgdorferi homologues of these genes. DNA sequence analysis revealed an open reading frame encoding a protein that is 62% identical to the E. coli DnaK protein. Genes homologous to the E. coli grpE and dnaJ genes, encoding products 28% and 39% identical to their homologues, are located up‐ and downstream, respectively, of the B. burgdorferi dnaK gene. No obvious promoters were detected in the sequenced DNA, although a potential transcription terminator was found downstream of the dnaJ gene, so these three genes may form an operon, perhaps with a fourth gene located upstream of the grpE gene. The grpE homologue complemented an E. coli grpE mutant and the dnaJ homologue complemented an E. coli dnaJ mutant, whereas the B. burgdorferi dnaK gene did not complement dnaK mutants.
Superinfection immunity of mycobacteriophage L5: applications for genetic transformation of mycobacteria
Authors: Donnelly‐Wu Mary K. , Jacobs William R. , Hatfull Graham F. 
Published: October 2006

SummaryMycobacteriophage L5 is a temperate phage of the mycobacteria that forms stable lysogens in Mycobacterium smegmatis. We show here that the 183‐amino‐acid product of L5 gene 71 confers immunity to L5 superinfection, is required for maintenance of the lysogenic state and contains a helix‐turn‐helix DNA‐binding motif—properties associated with repressors of temperate phages. We have utilized these observations to demonstrate the use of L5 gene 71 as a selectable marker for genetic transformation of the mycobacteria. Significantly, the use of L5 gene 71 as a selectable gene avoids the requirement for antibiotic‐resistance genes providing an important tool for manipulation of the pathogens Mycobacterium tuberculosis and Mycobacterium avium, and for the construction of recombinant BCG vaccines.
Iron‐dependent stability of the ferredoxin I transcripts from the cyanobacterial strains Synechococcus species PCC 7942 and Anabaena species PCC 7937
Authors: Bovy Arnaud , de Vrieze Geert , Lugones Luis , van Horssen Peter , van den Berg Claudia , Borrias Mies , Weisbeek Peter 
Published: October 2006

SummaryThe effect of iron on ferredoxin I specific mRNA levels was studied in the cyanobacterial strains Synechococcus sp. PCC 7942 (Anacystis nidulans R2) and Anabaena sp. PCC 7937 (Anabaena variabilis ATCC 29413). In both strains addition of iron to iron‐limited cells resulted in a rapid increase in ferredoxin mRNA levels. To investigate the possible role of the ferredoxin promoter in iron regulation, a vector for promoter analysis in Synechococcus PCC 7942 strain R2‐PIM9 was constructed, which contains the ferredoxin promoter fused to the gene encoding β‐glu‐curonidase (GUS) as reporter. Neither the Synechococcus nor the Anabaena ferredoxin promoter was able to direct iron‐regulated GUS activity in Synechococcus R2‐PIM9, Indicating that transcription initiation is not responsible for the iron‐dependent ferredoxin mRNA levels. Determination of the half‐life of the ferredoxin transcript in iron‐supplemented and iron‐limited cells revealed that, in both strains, the ferredoxin transcript is much more stable in iron‐supplemented cells than in iron‐limited cells. These results lead to the conclusion that in these strains, iron‐regulated expression of the ferredoxin I gene is mediated via differential mRNA stability.
Amplified expression of a transcriptional pattern formed during development of Anabaena
Authors: Wolk C. Peter , Elhai Jeff , Kuritz Tanya , Holland Doron 
Published: October 2006

SummaryThe cyanobacterium Anabaena responds to nitrogen deprivation by producing heterocysts, cells specialized for nitrogen fixation, at well‐spaced intervals along its filaments. The gene hepA, required for heterocyst maturation, is expressed in response to nitrogen deprivation, prior to visible differentiation. A spatial pattern of hepA expression indistinguishable from the eventual pattern of heterocysts was made visible by fusing the hepA promoter to luxAB, which encodes bacterial luciferase. Because the resulting signal did not greatly exceed instrumental background, T7 RNA polymerase was used to increase luminescence. The hepA promoter was fused to the gene for that polymerase, and a promoter recognized by that polymerase was fused to luxAB. Filaments containing these two fusions showed spaced luminescing cells many hours before differentiation became discernible morphologically.
Light‐induced carotenogenesis in Myxococcus xanthus: genetic analysis of the carR region
Authors: Hodgson David A. 
Published: October 2006

SummaryCarotenogenesis is light‐inducible in the non‐photo‐synthetic, Gram‐negative, bacterium Myxococcus xanthus. We report the characterization of the carR region which controls this phenomenon. Insertion of transposon Tn5 close to the carR region caused a dominant, carotenoid‐constitutive mutation because of the presence of a constitutive, outward‐reading promoter in the IS50L component of Tn5. In wild‐type cells, a powerful, tightly‐regulated, light‐inducible promoter directs the transcription of two genetic functions. One of these functions is to activate transcription of the genetically unlinked carB gene, which is involved in carotenoid synthesis. The second function (carR) regulates the light‐inducible promoter. We also report the mapping of two carotenoid constitutive mutations to the previously characterized car A locus.
Translational frameshifting in the control of transposition in bacteria
Authors: Chandler Michael , Fayet Olivier 
Published: October 2006

SummaryThe expression of an increasing number of genes of both prokaryotic and eukaryotic origin has been shown to be regulated at the translational level by programmed (sequence‐specific) ribosomal frame‐shifting. Among these are the bacterial insertion sequences IS1 and two members of the widely distributed IS3‐family, IS150 and IS911. Frameshifting provides a means of specifying several proteins with different functions using a minimum of genetic information. In this review, we survey present understanding of the way in which frameshifting is integrated into the overall control of transposition activity in these elements.
Class 1 outer membrane protein of Neisseria meningitidis: epitope analysis of the antigenic diversity between strains, implications for subtype definition and molecular epidemiology
Authors: McGuinness B. T. , Lambden P. R. , Heckels J. E. 
Published: October 2006

SummaryThe VR1 and VR2 regions of the class 1 protein have been sequenced from a number of meningococcal strains, including non‐subtypable strains and strains of apparently identical subtype. The amino acid sequences have been used to construct synthetic peptides for mapping subtype‐specific epitopes. The majority of epitopes was found to be located in VR2 at the apex of a predicted surface‐exposed loop. A single amino acid change within an epitope, or an amino acid deletion outside an epitope, were both associated with loss of subtype specificity, resulting from a change in the predicted conformation at the apex of the loop structure. Analysis of the sequence information combined with knowledge of defined epitopes also revealed considerable additional information not demonstrated by current subtyping procedures.
Bacterial interspersed mosaic elements (BIMEs) are present in the genome of Klebsiella
Authors: Bachellier Sophie , Perrin David , Hofnung Maurice , Gilson Eric 
Published: October 2006

SummaryBacterial interspersed mosaic elements (BIMEs) constitute a family of highly repetitive sequences containing palindromic units (PUs), also called repetitive extragenic palindromes (REPs). BIMEs were originally described in Escherichia coli and Salmonella typhimurium. We show here, by determining the nucleotide sequence of two intergenic regions of Klebsiella pneumoniae, by computer searches, and by hybridization, that sequences with similar characteristics are found in the genome of several Klebsiella species. This reinforces the idea that BIMEs play general and important roles in enterobacteria such as in the organization of the bacterial chromosome.
Characterization of a virG mutation that confers constitutive virulence gene expression in Agrobacterium
Authors: Jin Shouguang , Song Yan‐nong , Pan Shen Q. , Nester Eugene W. 
Published: October 2006

SummaryTransformation of plants by Agrobacterium tumefaciens is mediated by a set of virulence (vir) genes that are specifically induced by plant signal molecules through the VirA/VirG two‐component regulatory system. The plant signal is transmitted from VirA to VirG by a cascade of phosphorylation reactions followed by the sequence‐specific DNA binding of the VirG protein to the vir gene promoters which then activates their transcription. In this report, we describe a VirG mutant which is able to activate Wr gene expression independently of the VirA molecule and the two plant signal molecules, acetosyringone and monosaccharides. A strain of Agrobacterium containing this virG gene but lacking a functional virA gene was able to induce tumours on all three plants that were tested. A single amino acid change of asparagine (N) to aspartate (D) at position 54, adjacent to the site of VirG phosphorylation, aspartate 52, resulted in this constitutive phenotype. In vitro phosphorylation experiments showed that the mutant protein cannot be phosphorylated by VirA, suggesting that the negative charge resulting from the N to D switch mimics the phosphorylated conformation of the VirG molecule. The same amino acid change in the virG gene of the supervirulent strain A281 also resulted in a constitutive phenotype. However, the vir genes were not induced to high levels when compared with the levels of the constitutive Virg of strain A348.
High‐affinity binding of the basement membrane protein collagen type IV to the crystalline virulence surface protein array of Aeromonas salmonicida
Authors: Trust Trevor J. , Kostrzynska Magdalena , Emödy Levente , Wadström Torkel 
Published: October 2006

SummaryThe surface of the fish pathogen Aeromonas salmonicida is covered by a paracrystalline array (the A‐layer) which is a virulence factor for the organism. Quantification of the ability of A. salmonicida cells to bind collagen types I and IV in a 125I‐radiolabelled liquid‐phase assay showed that A‐layer‐positive cells bound high levels of collagen type IV, but significantly lower levels of collagen type I. Collagen type IV binding was confirmed using non‐radiolabelled enzyme‐linked immunosorbent assays. 125I‐Collagen type IV binding was rapid, specific, saturable, high affinity, and essentially irreversible by unlabelled collagen type IV. The A‐layer was responsible for collagen type IV binding because binding was inactivated by selective removal of the A‐layer at pH 2.2, and neither isogenic A‐layer‐deficient A. salmonicida mutants nor strains of Aeromonas hydrophila possessing a morphologically similar paracrystalline array bound this basement membrane protein.
The minCD locus of Bacillus subtilis lacks the minE determinant that provides topological specificity to cell division
Authors: Lee Soonyoul , Price Chester W. 
Published: October 2006

SummaryA key event of the sporulation process in Bacillus subtilis is the asymmetric cell division that divides the developing cell into two unequal compartments. To examine the function of vegetative cell division genes in this developmental division, we isolated and characterized the B. subtilis counterpart to the Escherichia coli minicell operon minB, which governs correct placement of the division septum. Starting from the closely linked spo/VFlocus, we used walking methods to isolate the region of the B. subtilis chromosome proximate to the divlVB minicell locus. DNA sequence analysis found two open reading frames whose predicted products had significant identity to the E. coli MinC cell division inhibitor and the MinD ATPase activator of MinC, and disruption of minCD function generated a minicell phenotype in B. subtilis. Notably, no homologue to the E. coli MinE topological specificity element was found in the B. subtilis minCD region. The B. subtilis min genes were part of an operon transcribed from a major promoter more than 2.5 kb upstream from minC. An internal promoter immediately upstream from minC was dependent on RNA polymerase containing sigma‐H and was active at the onset of sporulation. However, neither minCnor minD function was absolutely required for sporulation and, by implication, for asymmetric septum formation.
PilS and PilR, a two‐component transcriptional regulatory system controlling expression of type 4 fimbriae in Pseudomonas aeruginosa
Authors: Hobbs M. , Collie E. S. R. , Free P. D. , Livingston S. P. , Mattick J. S. 
Published: October 2006

SummaryTransposon mutagenesis was used to identify genes necessary for the expression of Pseudomonas aeruginosa type 4 fimbriae. In a library of 12 700 mutants, 147 were observed to have lost the spreading colony morphology associated with the presence of functional fimbriae. Of these, 28 had also acquired resistance to the fimbrial‐specific bacteriophage P04. The mutations conferring this phage resistance were found to have occurred at at least six different loci, including the three that had been previously shown to be required for fimbrial biosynthesis or function: the structural subunit (pilA) and adjacent genes (pilB,C,D), the twitching motility gene (pilT), and the Sigma 54 RNA polymerase initiation factor gene (rpoN). One novel group of phage‐resistant mutants was identified in which the transposon had inserted near sequences that cross‐hybridized to an oligonucleotide probe designed against conserved domains in regulators of RpoN‐dependent promoters. These mutants had no detectable transcription of pilA and did not produce fimbriae. A probe derived from inverse polymerase chain reaction was used to isolate the corresponding wild‐type sequences from a P. aeruginosa PAO cosmid reference library, and two adjacent genes affected by transposon insertions, pilS and pilR, were located and sequenced. These genes were shown to be capable of complementing the corresponding mutants, both at the level of restoring the phenotypes associated with functional fimbriae and by the restoration of pilA transcription. The pilSR operon was physically mapped to Spel fragment 5 (corresponding to about 72–75/0 min on the genetic map), and shown to be located approximately 25 kb from pilA–D. PilS and PilR clearly belong to the family of two‐component transcriptional regulatory systems which have been described in many bacterial species. PilS is predicted to be a sensor protein which when stimulated by the appropriate environmental signals activates PilR through kinase activity. PilR then activates transcription of pilA, probably by interacting with RNA polymerase containing RpoN. The identification of pilS and pilR makes possible a more thorough examination of the signal transduction systems controlling expression of virulence factors in P. aeruginosa.