摘要:

SummaryA‐factor, containing a γ‐butyrolactone in its structure, is an autoregulatory factor or a‘microbiai hormone’controlling secondary metabolism and cellular differentiation inStreptomyces griseus.A‐factor exerts its regulatory role by binding to a specific receptor protein which, in the absence of A‐factor, acts as a repressor‐type regulator for morphological and physiological differentiation, in the signal relay leading to streptomycin production inS. griseus, the A‐factor signal is transferred from the A‐factor receptor to the upstream activation sequence of a regulatory gene,strR, in the streptomycin biosynthetic gene cluster via an A‐factor‐dependent protein that serves as a transcription factor forstrR.The StrR protein thus Induced appears to activate the transcription of other streptomycin‐production genes. The presence of A‐factor homologues in a wide variety ofStreptomycesspecies and distantly related bacteria implies the generality of γ‐butyrolactones as chemical cellular signallin

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01073.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryTheRhsfamily comprises a set of composite elements found in the chromosomes of many naturalEscherichiacoli strains. FiveRhselements occur in strain K‐12. The most prominentRhscomponent is a giant core open reading frame (core ORF) whose features are suggestive of a cell surface ligand‐binding protein. This hypothetical protein contains a peptide motff, xxGxxxRYxYDxxGRL(I or T)xxxx, that is repeated 28 times. A similar repeated motif is found in aBacillus subtiliswall‐associated protein. TheRhscore ORFs consist of two distinct parts: a largeN‐terminal core that is conserved in allRhselements, and a smallerC‐terminus that Is highly variable. Distinctive G+C contents ofRhscomponents indicate that the elements have a recent origin outside theE. colispecies, and that they are composites assembled from segments with very different evolutionary histories. TheRhscores fail into three sub‐families that are mutually more than 20% divergent Downstream of the core ORF is a second, much shorter ORF. Like the adjacent core extension, these are highly variable. In most examples, the hypothetical product of this ORF has a candidate signal sequence for transport across the cytoplasmic membrane. AnotherRhscomponent, the 1.3 kb H‐rpt, has features typical of insertion sequences. Structures homologous to H‐rpt have been detected in other bacterial genera, such asVibrioandSalmonella, where they are associated with loci that determine O‐

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01074.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryStreptococcus pyogenesis 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 thevirRlocus. Most opacity factor‐positive (OF+) strains ofS. pyogenesalso express IgG Fc receptor proteins on their surface. These studies were initiated to determine whether the type IIa Fc receptor on the surface ofS. pyogenesphase‐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 thefcrAprobe at a greater dilution than that from their M−counterparts, (iv) Northern hybridization showed that thefcrAtranscript 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 withi

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01075.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

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 inBacillus 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 t

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01076.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe SEF14 gene cluster ofSalmonella enteritidiswas recently shown to contain three genes,sefABC, encoding a unique fimbrin, and proteins homologous to fimbrial chaperones and outer membrane proteins (ushers), respectively. A fourth open reading frame, designatedsefD, was found immediately downstream ofsefABCand overlappingsefC. The translated protein sequence ofsefDwas unique, but the composition was similar to that of other bacterial fimbriae. SefD was produced in abundance by wild‐typeS. enteritidisas shown by Western blot analysis using antibodies raised to affinity‐purified, recombinant SefD. Furthermore, unusually long, thin, fimbriae‐like structures were evident onS. enteritidisandEscherichia coliby immunoelectron microscopy, but in other bacterial species SefD was expressed as amorphous material. Therefore, inS. enteritidisandE. coli, SefD is the predominant structural subunit of SEF18. The SEF18 fimbriae‐like structures were shown to be serologically distinct from the three knownS. enteritidis fimbriaeSEF14, SEF17 and SEF21. Furthermore, SEF18 was still produced in set A insertion mutants, indicating that SEF14 and SEF18 were structurally distinct. Thus, the SEF14 gene cluster is the first example in the Enterobacteriaceae of a gene cluster that encodes two fimbrin‐like proteins, which are assembled into two distinct cell‐surface structures, SEF14 and SEF1B. DNA hybridization and Western blot analyses showed that SefD was widely distributed among the Enterobacteriaceae and was present inE. coli, Shigella, Enterobacter, Citrobacter, Erwinia, Hafnia, Klebsiella, Providencia, andProteusbut not in the non‐Enterobacteriaceae Gram‐negative bacteriaPseudomonas and Aeromonas, or in Gram‐positive bacteriaBacillusorStaphylococcus. Immunoelectron microscopy revealed that sefD was also present on the surface ofProvidenciaandKlebsiellabut did not appear filamentous. This is the first instance of highly conserved, thin fimbriaelike structers which are ubiquitous among the E

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01077.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryPrevious evidence showed that b‐ and a‐type flagellins ofPseudomonas aeruginosaare modifiedin vivoby phosphorylation at tyrosine. This research was designed to demonstrate phosphorylation of flageliin at tyrosinein 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

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01078.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryProtein L is a cell‐surface protein fromPeptostreptococcuswhich interacts with immunoglobulin kappa light chains. A gene fromPeptostreptococcusstrain 3316 coding for protein L and fragments thereof were expressed inEscherichia coli. The peptides were examined for binding to immunoglobulin and serum albumin. The four C units were shown to be responsible for binding to immunoglobulin and the four D units for binding to albumin. This protein L molecule therefore binds to albumin at a site separate from that involved in binding to immunoglobulin. The albumin‐binding units have high amino acid sequence identity with the albumin‐binding units of streptococcal cell‐surface proteins. The gene contains three sites available for internal initiation of translation resulting in three active proteins. The protein L molecule presented in this report was compared with a previously reported protein from Peptostreptococcus strain 312. The two proteins differ in several respects, including size and the number and types of repea

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01079.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

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 hos

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01080.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe Saccharomyces cersvislaeRAP1protein (Rap1p) is a key multifunctional transcription factor. Using gel retardation analysis, four binding sites forRAP1p have been identified within the promoter of theRAP1gene. These sites are located downstream of a binding site for the transcription factor Reb1p. The Reb1p site and an associated AT‐rich region are important for transcriptional activation, but deletion of three of theRAP1p‐binding sites had little effect on promoter activity. The activity of theRAP1promoter has been analysed in a yeast strain (YDS410) that contains a temperature‐sensitive mutation In theRAP1gene. This mutation renders the DNA‐binding activity of Rapip temperature dependent. When YDS410 was grown at a semi‐permissive temperature (30°C), the activity of theRAP1promoter increased by approximately 170%, compared with the same strain grown at the permissive temperature (25°C). ARAP1promoter in which three of the fourRAP1p‐binding sites had been deleted, showed only a small increase in activity in the same experiment. These data confirm that Rap1p is not required for activation of theRAP1gene, and suggest a role for Rap1p In negative au

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01081.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

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. syringaestra

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb01082.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY