摘要:

SummaryHaem O and/or haem A are specifically synthesized for the haem‐copper respiratory oxidases. A 17‐carbon hydroxyethylfarnesyl chain at the pyrrole ring A of the haems seems essential for catalytic functions at the oxygen‐reduction site. The discovery of haem O in the cytochrome bo complex from Escherichia coli was a breakthrough in the studies on haem A biosynthesis. Molecular biological and biochemical studies in the past three years demonstrated that thecyoE/ctaB/COX10genes are indispensable for functional expression of the terminal oxidases and encode a novel enzyme haem O synthase (protohaem IX farnesyltransferase). It has recently been suggested that the ctaA gene adjacent to the ctaB‐ctaCDEF gene cluster in Bacillus subtilis encodes haem A synthase (haem O monooxygenase). In this article, we review current knowledge of the genes for haem O and haem A biosyntheses, the location and regulation of haem O synthase, the possible enzymatic mechanism of farnesyl transfer to haem B and the possible roles of the farnesylate

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02174.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryPyelonephritic isolates ofEscherichia colicommonly express P‐pili, which mediate bacterial attachment to glycolipids on epithelial cell surfaces. Three classes of P‐pili have been defined, based on varying specificity for galabiose‐containing glycolipids. Variation in adhesive capacity is correlated with a shift in preferred host, suggesting that host tropism depends largely on detailed specificity for the globoseries glycolipids. In this study we examined the importance of the PapG adhesin in determining receptor specificity. Translational fusions were constructed between the ammo‐terminus of the PapG adhesin from each of the three pilus classes and a reporter protein. The binding specificity of the purified fusion proteinsin vitrowas identical to that seen with whole bacteria. Adherence of intact bacteria to cultured kidney cells was markedly reduced by a monoclonal antibody specific for the Class III adhesin (previously denotedPrsG), confirming the importance of the ammo‐terminus of PapG in mediating attachment to a receptor when presented on the eukaryotic cell surface. These results suggest that the detailed receptor specificity resides solely within the amino‐terminus of the PapG adhesin and is independent of the complex pilus a

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02175.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummarySpo0A is a phosphorylation‐activated transcription factor ofBacillus subtilis.It is a member of the response regulator super‐family of bacterial signal transduction proteins and controls many of the changes in gene expression that occur during the transition into stationary phase and during the initiation of speculation. To identify the domains of Spo0A most critical for determining its structural and functional features, presumptive homologues of thespo0Agene were characterized in a collection of eightBacillusspecies and sixClostridiumspecies representing phylogenetically diverse members of these genera. An alignment of the partial or complete DNA sequences of these homologues revealed three regions of especially high conservation in the effector domain. We speculate that the most highly conserved of these corresponds to the recognition helix of a putative helix‐turn‐helix motif, and, therefore, represents the actual DNA‐contacting surface of the protein. In the case of homologues identified inBacillus anthracisandClostridium acetobutylicumand retrieved by polymerase chain reaction amplification, we confirmed by gene‐disruption analysis that the homologue actually is required for initiation of sporulation. Apparent homologues of theB. subtilis spolVBgene were also discovered immediately upstream from thespo0Ahomologues in allBacillusandClostridiumspecies examined. The discovery of homologues ofB. subtilissporulation genes in these diverse species implies that the gene products required for specifying pathways of sporulation‐specific gene activation and for determining key morphogenetic changes may be highly conserved and suggests that an approach similar to that undertaken here might be used as a general strategy to retrieve and compare their gene sequences. Exhaustive efforts to detect a spo0A‐like gene in non‐endospore formers, including close relatives ofBacillussuch asListeriaandStaphylococcus, were uniformly unsuccessful, suggesting that regulation of gene activity during the transition into stationary phase mediated by Spo0A‐like proteins may be exclusive to the endospo

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02176.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryMost of the genes required for the conjugative transfer of DNA are encoded by the 33 kb transfer (tra) operon of F‐like conjugative plasmids. Transcription of the tra operon is positively regulated by the TraJ transcriptional activator which, in turn, is negatively regulated by the FinOP fertility inhibition system. The FinOP system consists of an antisense RNA, FinP, and a 21.2 kDa protein, FinO, which together inhibit TraJ expression. Previously, it has been demonstrated that FinO increases thein vivostability of the FinP RNA in the absence of thetraJmRNA target. Using electrophoretic mobility shift assays, we have shown that FinO is an RNA‐binding protein that binds to one of the two stem‐loops in FinP and to its complementary structure intraJ mRNA. This interaction presumably protects FinP RNA from degradationin vivoand increases the rate of formation of the FinP‐traJmRNA duplex fivefold. Thus, TraJ expression appears to be influenced by a unique RNA‐protein interaction that precedes duplex formation between the FinP anti‐sense RNA and its tar

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02177.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryRetrons are genetic elements that encode multicopy single‐stranded DNAs called msONAs. They are clonally distributed inEscherichia coliand retrons in different clones produce DNAs with different nucleotide sequences. msDNAs consist of an RNA molecule covalently linked to a single‐stranded DNA molecule. The latter contains an inverted repeat, resulting in a stem‐loop structure. In two retrons, Ec83 and Ec78, the DNA is cleaved off from the RNA. All known retrons except Ec78, have one or more mismatched base pairs in the stem‐loop structure. We found that two retrons, Ec86 and Ec83, when present in high copy numbers are mutagenic. The ratios of mutation frequencies observed in Lac indicator strains were similar to the ratios observed for a mutant defective in mismatch repair. It is known that some proteins required for mismatch repair bind to mismatched base pairs prior to carrying out repair. The similarity in the mutation frequency ratios suggested that the mutagenesis caused by msDNAs of retrons Ec86 and Ec83 might be due to seqestration of a mismatch repair protein by msDNA. Strong support for this interpretation was obtained from the finding that the msDNA produced by retron Ec78 is not mu

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02178.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryCurli are fimbrial structures expressed byEscherichia colithat specifically interact with matrix proteins such as fibronectin and laminin. Similar structures are also expressed bySalmonella enteritidisand have been denoted thin aggregative fimbriae. Bacteria expressing curli and thin aggregative fimbriae were found to bind radiolabelled plasminogen as well as the tissue‐type plasminogen activator (t‐PA). By contrast,E. colicarrying a gene locus with an insertionally inactivated chromosomal curlin subunit were unable to bind the two human proteins. The purified subunit polypeptides of curli and thin aggregative fimbriae bound plasminogen and t‐PA with high affinity (1 × 108to 2 × 108M‐1). The binding of plasminogen and t‐PA to curli‐expressingE. coliwas only partially inhibited by fibronectin and laminin. Plasminogen absorbed from human plasma by curli‐expressingE. coliwas readily converted to plasmin by t‐PA; both plasmin and t‐PA were functionally active when bound to the bacteria. A simultaneous binding of fibrinolytic proteins and matrix proteins to fimbriae ofE. coliand S.enteritidiscould provide these pathogens with both adhesive and

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02179.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryCampylobacter fetusutilizes paracrystalline surface (S‐) layer proteins that confer complement resistance and that undergo antigenic variation to facilitate persistent mucosal colonization in ungulates.C. fetuspossesses multiple homologues ofsapA, each of which encode full‐length S‐layer proteins. Disruption ofsapAby a gene targeting method (insertion of kanamycin (km) resistance) caused the loss ofC. fetuscells bearing full‐length S‐layer proteins and their replacement by cells bearing a 50 kDa truncated protein that was not exported to the cell surface. After incubation of the mutants with serum, the survival rate was approximately 2 × 10‐2. Immunoblots of survivors showed that phenotypic reversion involving high‐level production of full‐length (98, 127 or 149 kDa) S‐layer proteins had occurred. Revertants were serum resistant but caused approximately 10‐fold less bacteraemia in orally challenged mice than did the wild‐type strain. Southern hybridizations of the revertants showed rearrangement ofsapAhomologues and retention of thekmmarker. These results indicate that there exists high‐frequency generation ofC. fetus sapAantigenic variants, and that intracellular mechanisms acting at the level of DNA reciprocal recombination play key

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02180.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummarypAMβ1 is a low‐copy‐number, promiscuous plasmid from Gram‐positive bacteria that replicates by a unidirectional theta‐type mode. Its replication is initiated by an original mechanism, involving the positive rate‐limiting RepE protein. Here we show that the pAMβ1‐encoded CopF protein is involved in negative regulation of the plasmid copy number. CopF represses ‐10‐fold the transcription initiated at the promoter of therepEgene and binds to a 31 bp segment which is located immediately upstream of the ‐35 box of therepEpromoter. We propose that CopF inhibits initiation of transcription at therepEpromoter by bind

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02181.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe amount of the rate‐limiting replication initiator protein RepR of plasmid p1P501 is negatively controlled by an antisense RNA (RNAIII) and a dispensable protein (CopR). Deletions or mutations in either component cause a 10‐20‐fold copy number increase. RNAIII induces transcription attenuation of therepRmRNA: the mode of CopR action remained unclear. To test the function of CopR, transcriptional fusions of promoters pI, pII and pIII withlacZwere integrated into theBacillus subtilischromosome. CopR and/or RepR were suppliedin trans, and LacZ synthesis measured. The results show that CopR represses therepRpromoter pII. Neither CopR nor RepR autoregulate their promoters. Gel mobility shift assays indicate that CopR binds to a 44 bp DNA fragment comprising the inverted repeat upstream o

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02182.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryDevelopment of theEscherichia colicell division site was studied in wild‐type cells and in non‐septate filaments offtsZnull andftsZTs mutant cells. Localized regions of plasmolysis were used as markers for the positions of annular structures that are thought to be related to the periseptal annuli that flank the ingrowing septum during cytokinesis. The results show that these structures are localized at potential division sites in non‐septate filaments of FtsZ‐cells, contrary to previous reports. The positions of the structures along the long axis of the cells in both wild‐type cells and FtsZ‐filaments were unaffected by the presence of plasmolysis bays at the cell poles. These results do not agree with a previous suggestion that the apparent association of plasmolysis bays with future division sites was artefactual. They support the view that division sites begin to differentiate before the initiation of septal ingrowth and that plasmolysis bays and the annular attachments that define them, mark the locations of these early events in the divis

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1994.tb02183.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY