bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of rpoS (katF) in oxyR‐independent regulation of hydroperoxidase I in Escherichia coli
Authors: Ivanova Anna , Miller Cathy , Glinsky Gennadi , Eisenstark Abraham 
Published: October 2006

SummaryWe present evidence showing that rpoS (katF) is a regulator of katG gene transcription In an oxyR‐independent manner. Mutation of the rpoS gene in several different Escherichia coli strains caused a significant reduction in catalase HPI activity. In rpoSδoxyR double mutants, the level of HPI was considerably lower compared to the δoxyR parent strain, and was restored when transformed with an rpoS+ plasmid. Overproduction of HPI in oxyR suppressor strains was greatly diminished after inactivation of the rpoS gene and was accompanied by a substantial increase in sensitivity to menadione. Beta‐galactostdase expression from a katG::lacZ promoter was lower in rpoS strains compared to rpoS+ isogenic parents. Several δoxyR strains had detectable levels of katG transcription that was significantly diminished after rpoS gene inactivation.
Identification of lactoferrin‐binding proteins from Treponema pallidum subspecies pallidum and Treponema denticola
Authors: Staggs Teanna M. , Greer Margaret K. , Baseman Joel B. , Holt Stanley C. , Tryon Victor V. 
Published: October 2006

SummaryLactoferrin‐binding or ‐associated proteins were identified in Treponema pallidum subspecies pallidum and Treponema denticola by affinity column chromatography using human lactoferrin and detergent‐solubilized, radiolabelled spirochaetes. Two discrete polypeptides of T. pallidum with masses of 45 and 40kDa and a broad band from 29‐34 kDa exhibited association with human apo‐ and partially ferrated lactoferrin. T. denticola produced two proteins that associated with a lactoferrin affinity matrix (50 and 35 kDa). T. pallidum and T. denticola did not associate with soluble, human transferrin in parallel experiments. Soluble human lactoferrin competed with all lactoferrin‐associated proteins from T. pallidum and T. denticola in competitive‐binding assays. However, the T. denticola proteins dissociated from a lacto‐ferrin‐affinity matrix in the presence of differing concentrations of unlabelled, soluble lactoferrin competitor. Treatment with phospholipase D altered migration of the diffuse 29‐34 kDa band of T. pallidum suggesting that the polypeptide was lipid‐modified. Each of the lactoferrin‐binding proteins from T. pallidum and T. denticola reacted with pooled rabbit syphilitic antisera. The lactoferrin‐binding proteins of T. pallidum reacted with human sera from patients at all stages of syphilis. In addition, a monoclonal antibody generated against the 45 kDa polypeptide of T. pallidum crossreacted with the 29–34 kDa protein.
‘Muprints’ of the lac operon demonstrate physiological control over the randomness of in vivo transposition
Authors: Wang Xiuhua , Higgins N. Patrick 
Published: October 2006

SummaryA method called Muprinting has been developed that uses PCR to generate a detailed picture of the bacteriophage Mu transposition sites in chosen domains of the bacterial chromosome. Muprinting experiments In Escherichia coli show that the frequency of phage integration changes dramatically near two repressor binding sites in the lac operon. When the lac operon was repressed, hotspots for Mu transposition were found near the O1 and O2 operators that are proposed to make a repression loop. When cells were grown in lactose, Mu transposition near these operators was greatly diminished. Striking changes In transposition frequencies were limited to the control region and were not found in a region of the lacZ gene lying beyond the O2 operator. Muprints of the bgl operon showed a different pattern; hotspots for Mu transposition detected in sequences upstream of the bglC promoter when the operon was silenced changed when the operon became activated by mutation. By targeting transposition to the regulatory regions around non‐expressed genes, Mu may demonstrate a self‐restraint mechanism that allows the virus to move through its host genome without disrupting the functions that contribute to a healthy cell physiology.
Protein folding in the periplasm of Escherichia coli
Authors: Wülfing Christoph , Plückthun Andreas 
Published: October 2006

SummaryWith the discovery of molecular chaperones and the development of heterologous gene expression techniques, protein folding in bacteria has come into focus as a potentially limiting factor in expression and as a topic of interest in its own right. Many proteins of importance in biotechnology contain disulphide bonds, which form in the Escherichia coli periplasm, but most work on protein folding in the periplasm of E. coli is very recent and is often speculative. This MicroReview gives a short overview of the possible fates of a periplasmic protein from the moment it is translocated, as well as of the E. coli proteins involved in this process. After an introduction to the specific physiological situation in the periplasm of E. coli, we discuss the proteins that might help other proteins to obtain their correctly folded conformation — disulphide isomerase, rotamase, parts of the translocation apparatus and putative periplasmic chaperones — and briefly cover the guided assembly of multi‐subunit structures. Finally, our MicroReview turns to the fate of misfolded proteins: degradation by periplasmic proteases and aggregation phenomena.
A group A streptococcal Enn protein potentially resulting from intergenomic recombination exhibits atypical immunoglobulin‐binding characteristics
Authors: Podblelski A. , Hawlitzky J. , Pack T. D. , Flosdorff A. , Boyle M. D. P. 
Published: October 2006

SummaryThe gene encoding the Enn protein (enn) of the M untypeable group A streptococcal (GAS) strain 64/14 was amplified by polymerase chain reaction, cloned into the expression vector pJLA602 and expressed in Escherichia coli DH5α. Unlike other GAS–Enn proteins, which exhibit IgA‐binding activity, the recombinant Enn enn64/14 protein reacted preferentially with human IgG3. The 1050 bp open reading frame comprising the enn64/14 gene was completely sequenced. The region of the gene encoding the signal peptide and the C‐terminus exhibited >95% homology to corresponding sections of other enn genes. The region of enn64/74 encoding the N‐terminus of the mature Enn protein was found to be highly homologous to the corresponding section of the gene encoding the M‐like protein of GAS serotype M9 (emmL9). The reoombinant protein encoded by emmL9 was found to react with all four human IgG subclasses. About 30% of the 1152bp open reading frame of emmiL9 encoding the N‐terminus was found to display >90% homology to the corresponding section of enn64/14 but was <50% homologous in the remainder of the gene sequence. The functional analysis of the subcloned N‐terminal section of emmL9 demonstrated a polypeptide exhibiting selective binding to human IgG3. These findings suggested that enn64/14 was a hybrid gene formed by recombination of an enn gene and an emmL9 gene. The putative recombinational event could have Involved a set of flanking 7bp direct repeats. Since enn64/14 and emmL9 are genes from different phylogenetic lineages of GAS, this report provides evidence that intergenomic recombinations between different types of GAS genes can occur and could lead to hybrid proteins with unique Ig‐binding characteristics.
Identification and molecular analysis of a locus that regulates extracellular toxin production in Clostridium perfringens
Authors: Lyristis Michael , Bryant Amy E. , Sloan Joan , Awad Milena M. , Nisbet Ian T. , Stevens Dennis L. , Rood Julian I. 
Published: October 2006

SummaryThe anaerobic bacterium Clostridium perfringens mediates clostridial myonecrosis, or gas gangrene, by producing a number of extracellular toxins and enzymes. Transposon mutagenesis with Tn916 was used to isolate a pleiotropic mutant of C. perfringens that produced reduced levels of phospholipase C, protease and sialidase, and did not produce any detectable perfringolysin O activity. Southern hybridization revealed that a single copy of Tn916 had inserted into a 2.7 kb Hindlll fragment in the C. perfringens chromosome. A 4.3 kb Pstl fragment, which spanned the Tn916 insertion site, was cloned from the wild‐type strain. When subcloned into a shuttle vector and introduced into C. perfringens this fragment was able to complement the Tn916‐derived mutation. Transformation of the mutant with plasmids containing the 2.7 kb Hindlll fragment, or the 4.3 kb Pstl fragment resulted in toxin and enzyme levels greater than or equal to those of the wild‐type strain. The Pstl fragment was sequenced and found to potentially encode seven open reading frames, two of which appeared to be arranged in an operon and shared sequence similarity with members of two‐component signal transduction systems. The putative virR gene encoded a protein with a deduced molecular weight of 30140, and with sequence similarity to activators in the response regulator family of proteins. The next gene, virS, into which Tn916 had inserted, was predicted to encode a membrane‐spanning protein with a deduced molecular weight of 51 274. The putative VirS protein had sequence similarity to sensor proteins and also contained a histidine residue highly conserved in the histidine protein kinase family of sensor proteins. Virulence studies carried out using a mouse model implicated the virS gene in the pathogenesis of histotoxic C. perfringens infections. It was concluded that a two‐component sensor regulator system that activated the expression of a number of extracellular toxins and enzymes involved In virulence had been cloned and sequenced. A model that described the regulation of extracellular toxin production in C. perfringens was constructed.
Regulation of spvR gene expression of Salmonella virulence plasmid pKDSC50 in Salmonella choleraesuis serovar Choleraesuis
Authors: Abe A. , Matsui H. , Danbara H. , Tanaka K. , Takahashi H. , Kawahara K. 
Published: October 2006

SummaryThe expression regulation of spvR, a regulatory gene on the virulence plasmid (pKDSC50) of Salmonella choleraesuis serovar Choleraesuis, was investigated by spvR–lacZ translational fusion. The spvR gene was found to be positively regulated by its own product, the SpvR protein, and this unusual positive auto‐regulation was repressed by the products of spvA and spvB, virulence‐associated genes present downstream from the spvR gene. Amino acid sequence analysis revealed that the amino‐terminal region of SpvB had homology with the CatM repressor protein of Acineto‐bacter calcoaceticus, which belongs to the MetR/LysR protein family. On the other hand, the sigma factor RpoS was required for expression of the spvR gene in the stationary phase of bacterial growth. The SpvR protein was also necessary for self‐activation, suggesting that an RNA polymerase holoenzyme containing RpoS requires SpvR protein in order to recognize the spvR promoter.
Generalized transposon shuttle mutagenesis in Neisseria gonorrhoeae: a method for isolating epithelial cell invasion‐defective mutants
Authors: Kahrs Andreas F. , Bihlmater Armin , Facius Dirk , Meyer Thomas F. 
Published: October 2006

SummaryOne requirement for the invasion of, and tight adherence to, human epitheiial cells by Neisseria gonorrhoeae is the synthesis of distinct opacity (Opa) outer membrane proteins, encoded by a family of phase‐variable chromosomal genes. However, cloning and surface expression of invasion‐promoting Opas in Escherichia coli is not sufficient for the efficient invasion of epithelial cells: additional factors besides Opa may be involved in this process. Using the phoA mini‐transposon TnMax4, a library of gonococcal mutants affected in the expression of genes encoding exported proteins was generated through shuttle mutagenesis. Of a total of 608 PhoA+ plasmid clones identified in E. coli E145 approximately 40% were used successfully in transforming N. gonorrhoeae and in activating the corresponding chromosomal genes. Gonococci producing the invasion‐promoting Opa50 served as the genetic background to identify 51 mutants unable to enter Chang human epithelial cells. We expect some of these mutations affect the interaction of N. gonorrhoeae with epithelial cells directly, while other mutants may carry defects in general house‐keeping, secretory and/or regulatory determinants. In some mutants the loss of invasiveness appears to be due to a negative dominant effect of the PhoA+ fusions produced in these mutants. Some of the identified genes display a phase‐variation phenomenon in E. coli and several genes are found in multiple copies in N. gonorrhoeae and/or present only in pathogenic Neisseria species.
Streptococcus pyogenes type IIa IgG Fc receptor expression is co‐ordinately regulated with M protein and streptococcal C5a peptidase
Authors: La Penta Diqui , Zhang Xin Pin , Cleary P. Patrick 
Published: October 2006

Summary Streptococcus pyogenes is an important agent of human disease which expresses a variety of proteins and polysaccharides on its surface. Surface molecules M protein and streptococcal C5a peptidase (SCPA) are virulence factors which undergo concurrent phase variation and are under the co‐ordinate control of the virR locus. Most opacity factor‐positive (OF+) strains of S. pyogenes also express IgG Fc receptor proteins on their surface. These studies were initiated to determine whether the type IIa Fc receptor on the surface of S. pyogenes phase‐varies with members of this regulatory circuit. Several methods were applied to M− and M− variant strains to evaluate this question, (i) Immunoblot assays quantified Fc receptors on whole cells by using human IgG myeloma protein and receptor‐specific antibody. M− strains bound IgG and antibody specific for Fc protein, whereas M− strains did not. (ii) Enzyme‐linked immunosorbent assays quantified Fc receptor antigen expression and showed that M+ strains produce more Fc receptor protein than their M− derivatives, (iii) Quantitative RNA dot blots showed that the message for the Fc receptor gene (fcrA) was reduced in M− strains. RNA from M+ strains hybridized to the fcrA probe at a greater dilution than that from their M− counterparts, (iv) Northern hybridization showed that the fcrA transcript is 1200 nucleotides in size and distinct from transcripts for M and SCPA proteins. These data are evidence for the co‐ordinate transcriptional control of the Fc receptor, M protein, and SCPA and show that these proteins co‐ordinately phase‐vary within the same regulatory circuit.
Peptide permeases modulate transformation in Streptococcus pneumoniae
Authors: Pearce B. J. , Naughton A. M. , Masure H. R. 
Published: October 2006

SummaryTo Identify elements participating In the process of transformation, a bank of genetically altered mutants of Streptococcus pneumoniae with defects in exported proteins was assessed for a decrease in transformation efficiency. One mutant consistentiy transformed 10‐foid less than the parent strain. Sequence analysis and reconstitution of the altered locus revealed a gene, plpA (permease‐like protein), which encodes a putative substrate‐binding protein belonging to the family of bacterial permeases responsible for peptide transport. The derived amino acid sequence for this gene was 80% similar to AmiA, a peptide‐binding protein homologue from pneumococcus, and 50% similar over 230 amino acids to SpooKA which is a regulatory element in the process of transformation and sporulation in Bacillus subtilis. PIpA fusions to alkaline phosphatase (PhoA) were shown to be membrane associated and labelled with [3H]‐palmitic acid, which probably serves as a membrane anchor. Experiments designed to define the roles of the pIpA and ami determinants in the process of transformation showed that: (i) mutants with defects in plpA were >90% transformation deficient while ami mutants exhibited up to a fourfold increase in transformation efficiency; (ii) compared to the parental strain, the onset of competence in an ami mutant occurred earlier in logarithmic growth, whereas the onset was delayed in a plpA mutant; and (ill) the plpA mutation decreases the expression of a competence‐regulated locus. Since the permease mutants would fail to bind specific ligands, it seems likely that the substrate‐permease interaction modulates the process of transformation.
Tyrosine kinase activity in Pseudomonas aeruginosa
Authors: South Suzanne L. , Nichols Robert , Montie Thomas C. 
Published: October 2006

SummaryPrevious evidence showed that b‐ and a‐type flagellins of Pseudomonas aeruginosa are modified in vivo by phosphorylation at tyrosine. This research was designed to demonstrate phosphorylation of flageliin at tyrosine in vitro. Evidence presented showed that flageilin is labelled by [γ‐32P]‐ATP, but not by [α‐32P]‐ATP, when incubated with cell envelope fractions. Results suggested that autophosphoryiation of a 42 kDa membrane protein occurred. No activity was detected in cytoplasmic fractions. Flagellin protein was identified by flagella‐specific monoclonal antibody (mAb) and was labelled with anti‐phosphotyrosine mAb. Confirmation of tyrosine kinase activity was shown by labelling of synthetic poly (Glu:Tyr) as a substrate with [γ‐32P]‐ATP. Labelling of poly (Glu:Tyr) was heat sensitive and time dependent. Labelled phosphotyrosine was observed in partial acid hydrolysates of substrates. Using poly (Glu:Tyr) as substrate, tyrosine kinase activity was shown to be inhibited by sulphydryl reagents. It appears that tyrosine kinase and flagellin phosphorylation occur in several Pseudomonas spp. Location of phosphotyrosine in a conserved region of flagellin may serve as a cell signal so that intact flagellin is appropriately exported.
Targeted mutagenesis of the phospholipase D gene results in decreased virulence ofCorynebacterium pseudotuberculosis
Authors: McNamara Peter J. , Bradley Gregory A. , Songer J. Glenn 
Published: October 2006

SummaryThe chromosomal gene encoding the phospholipase D fromCorynebacterium pseudotuberculosis(biovar ovis) isolate Whetten 1 was replaced with an allele containing a nonsense mutation. The virulence of the mutant strain (W1.31r1) and the isogenic parental strain were then compared by inoculation of goats. The with‐type strain caused abscessation at the site of infection, which then spread to the regional lymph node, while W1.31r1 had a reduced ability to establish a primary infection and was incapable of dissemination. Our results confirm that phospholipase D is a virulence determinant ofC. pseudotuberculosisthat increases the persistence and spread of the bacteria within the host.
Two native plasmids ofPseudomonas syringaepathovar tomato strain PT23 share a large amount of repeated DNA, including replication sequences
Authors: Murillo Jesus , Keen Noel T. 
Published: October 2006

SummaryStrain PT23 ofPseudomonas syringaepv, tomato contains four native plasmids, designated A, B, C, and D. By DNA hybridization of genomic and plasmid DNA digests from the wild type and a plasmid‐cured strain, we determined thatc. 61 kb (c.74%) of pPT23B is repeated in pPT23A and onlyc.17 kb (c.21%) is in single copy in strain PT23. pPT23B also contains DNA repeated in the chromosome that occurs in three DNA fragments of 0.6, 4.6, and 9.6 kb that might be transposable elements. Additionally, the 9.6 kb fragment also shares sequences with the three other plasmids of strain PT23. By DNA hybridization with the origin of replication from a native plasmid ofP. syringaepv. syringae andin vivoreplication tests, we identified the origins of replication of plasmids A, B, and D and showed that they cross‐hybridize. The putative par region from pPT23 A has also been identified and is not conserved in the other three native plasmids from strain PT23. By using the defined minimal origin of replication from pPT23 A as a probe, we showed that it is highly conserved in 14 strains belonging to nine different pathovars ofP. syringaeand that as many as five different native plasmids with closely related origins of replication coexist in the same cell. The duplication and reorganization of plasmids might therefore occur at high frequency and could be responsible for the existence of large numbers of native plasmids inP. syringaestrains.
The interaction of a recombinant cecropin/melittin hybrid peptide with the outer membrane of Pseudomonas aeruginosa
Authors: Piers K. L. , Hancock R. E. W. 
Published: October 2006

SummaryA cecropin/melittin hybrid peptide (CEME) produced by recombinant DNA procedures was tested for its ability to interact with the outer membrane of Pseudomonas aeruginosa and found to have identical biological properties to that of chemically synthesized CEME. CEME was shown to kill P. aeruglnosa and permeabilize its outer membrane to lysozyme and 1‐N‐phenylnaphthlyamine, in some cases better than other antimicrobial agents and permeabilizers. CEME demonstrated a high‐binding affinity to purified P. aeruginosa lipopolysaccharide (LPS) and LPS in whole‐cell environments. These data provide information on the molecular mechanism of CEME antimicrobial activity and strongly suggest that it is taken up across the outer membrane by the self‐promoted uptake pathway.
Regulation of acetyl phosphate synthesis and degradation, and the control of flagellar expression in Escherichia coli
Authors: Prüβ Birgtt M. , Wolfe Alan J. 
Published: October 2006

SummaryWe investigated the relationship between Escherichia coli flagellar expression and the regulation of acetyl phosphate synthesis and degradation. Using cells either wild type for acetyl phosphate metabolism or defective for phosphotransacetylase or acetate kinase, or both, we measured flagellar expression and the intracellular concentration of acetyl phosphate relative to growth phase and temperature. Under the conditions tested, we found that elevated levels of acetyl phosphate corresponded to inhibition of flagellar synthesis. To extend these observations, we measured the intracellular concentration of acetyl‐CoA, the level of expression from the pta and ackA promoters, and the activities of phosphotransacetylase and acetate kinase derived from cell lysates. Relative to increasing culture density, acetyl‐CoA levels and expression from both the pta and ackA promoters decreased. Relative to Increasing temperature, expression from the ackA promoter decreased and phosphotransacetylase activity increased. In contrast, temperature had little or no effect on either acetate kinase activity or expression from the pta promoter. We propose that cells regulate intracellular acetyl phosphate concentrations relative to growth phase and temperature by modulating the availability of acetyl‐CoA, the expression of ackA, and the activity of phosphotransacetylase.