摘要:

SummaryCitrate‐dependent Fe3+transport intoEscherichia coliK‐12 is induced by iron and citrate. The inducer is probably ferric dicitrate which does not have to be taken up into the cytoplasm to induce transcription of thefectransport genes. Two regulatory genes,fed and fecR, located upstream of thefecABCDEtransport genes, are required for induction. We report thatin vivothe chromosomally encoded Feel protein activates transcription of thefecAandfecBtransport genes in response to ferric citrate and the FecR protein. Cells expressing chromosomally and plasmid‐encoded truncated FecR derivatives no longer responded to ferric citrate and expressed thefectransport genes constitutively. The smallest active FecR derivative contained 59 amino acid residues as compared to the 317 residues of wild‐type FecR. Constitutive induction was lower than induction of the FecR wild‐type strain by ferric citrate. It is concluded that theN‐terminal portion of FecR activates Feel and that theC‐terminal portion of FecR responds to ferric citrate. Transcription of the fee transport genes is positively regulated by Feel and FecR and negatively regulated by the Fe2+‐Fur repressor. Transcription activation and repression may occur independentl

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02226.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe kinetics of reinitiation of chromosome replication of eightdnaA(Ts)mutants was investigated in an isogenic set of strains. Five mutants (167, 46, 601, 606 and 5) are classified as reversible, since they can reinitiate at 30 C without protein synthesis, whereas the other three (508, 205, 204) require protein synthesis. In the presence of protein synthesis, reversible mutants initiate one round of replication rapidly after a shift to 30δC, indicating that they contain active or renaturable DnaA protein. ThednaA508anddnaA204mutants also reinitiate chromosome replication rapidly, whereas reinitiation is delayed 15–20min indnaA205.ThednaA508anddnaA204mutants might contain active DnaA protein just below the threshold level at 42δC and only require synthesis of small amounts of new DnaA protein before initiation at 30δC, whereasdnaA205accumulates DnaA protein for some time at 30δC before reaching the initiation threshold. Three of the reversible mutants (5, 601, and606) exhibited, in addition to the protein synthesis‐independent initiation capacity, an RNA synthesis‐independent initiation capacity. The thermal stability of these initiation capacities is the same as for mutant DnaA protein, strongly suggesting that mutant DnaA protein is responsible

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02227.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThednaA204mutant, one of the so‐called irreversiblednaAmutants which cannot reinitiate chromosome replication upon a shift from non‐permissive to permissive growth temperature in the absence of protein synthesis, was reinvestigated using flow cytometry and marker frequency analysis. In a temperature downshift experiment and in the presence of protein synthesis thednaA204mutant reinitiates chromosome replication very fast. Using alacpromoter‐controlled wild type or adnaA204mutant gene carried on a plasmid, we have observed instantaneous initiation of replication when synthesis of DnaA protein is induced in thednaA204mutant at 42δC. The data indicate that thednaA204mutant after a shift to 42δC still contains functional DnaA protein, but that the activity level is below the initiation threshold. Thus, after synthesis of very small amounts of additional DnaA protein, initiation occurs very fast both after a shift to 30δC, and after induction of DnaA protein synthesis at 42 C. A model describing the processing of DnaA protein in mutants and in the wild type Is p

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02228.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe kinetics of initiation of chromosome replication after induction of DnaA protein synthesis was studied in adnaA(null) rnhmutant ofEscherichia coli.DnaA protein synthesis was induced to different extents using the wild‐typednaAgene controlled by alacpromoter. Initiation of chromosome replication fromoriC, measured as an increase in origin to terminus ratio, took place at different times after addition of an inducer dependent on the DnaA protein synthesis rate. The first initiations always occurred when DnaA protein had accumulated approximately to the average wild‐type concentration (24 ng of DnaA protein per ml cells at OD450= 1.0) At a low DnaA protein accumulation rate one synchronous round of replication was obtained after 30min of induction. The initiation kinetics obtained when DnaA protein accumulated rapidly was complicated and indicated that other factors might also be invol

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02229.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe right part of thehrpcluster ofPseudomonas syringaepv.phaseolicolacontains two regulatory genes, the previously describedhrpSgene and an adjacent locus,hrpR.In this study we determined the sequence ofhrpRand analysed the functional organization of the two genes. HrpR and HrpS show high sequence similarities to each other and to other response regulators of the two‐component regulatory system. This has recently also been described for thehrpRSsystem of the closely related pathogenPseudomonas syringaepv.syringae.The results of our genetic analyses strongly indicate thathrpSexpression is regulated by thehrpRgene product. DNA‐protein binding studies and site‐directed mutagenesis of thehrpRsequence provided further evidence that HrpR activateshrpStranscription by binding to an activator site. This HrpR binding site has mapped in a fragment which is located 378–609 nucleotides upstream of thehrpStranscription start site. ThehrpStranscription start site maps 179 nucleotides upstream of the initiation codon ATG, as determined by primer extension analysis, and is preceded by a typical ‐12/‐24 pro

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02230.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryTheARO3gene ofSaccharomyces cerevisiaecodes for the phenylalanine‐inhibited 3‐deoxy‐d‐arabino‐heptulosonate‐7‐phosphate synthase (EC 4.1.2.15) and is regulated by the general control system of amino acid biosynthesis through a single GCN4‐binding site in its promoter. A combined deletion and mutation analysis of theARO3promoter region in a δgcn4‐background revealed two additional regulatory systems involved inARO3transcription. TheARO3gene is (i) activated through a sequence element which binds the multifunctional DNA‐binding protein ABF1in vitroand (ii) repressed through an URS1 element, which binds the same proteinin vitroas the URS1 element In theCAR1promoter. Since both the ABF1‐binding site and the URS1 element representcis‐actingelements of global transcription regulatory systems in yeast, theARO3gene is the first example of a GCN4‐regulated gene which is both activated and repressed by global transcription factors. Activation of theARO3gene through the ABF1‐binding site and repression through the URS1 element seem to be independent of each other and independent of ac

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02231.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryGene cassettes are mobile DNA elements which contain a specific recombination site, a 59‐base element, recognized by the site‐specific recombination system of integrons. Gene cassettes are normally found inserted at a unique site in an integron, downstream of a promoter which directs transcription of the cassette‐associated genes. However, insertion of a gene cassette into a secondary site in a plasmid which does not contain an integron is also formally possible. Sequence analysis of theaadBgene in pIE723, a plasmid closely related to the IncQ plasmid RSF1010, revealed the presence of the completeaadBcassette inserted at a secondary site downstream of a known RSF1010 promoter. The site of insertion of theaadBcassette in RSF1010 conformed to the consensus for secondary sites recognized by the integron integrase (int), and it is likely that the cassette was inserted via a single Int‐mediated recombination event between the 59‐base element of a free, circularaadBcassette and a secondary site in RSF1010. The cassette‐associated recombination site was inactivated by the insertion, and Int‐mediated excision of theaadBcassette from this non‐specific location was not detectable, indicating that the cassette is stably inserted. The movement of gene cassettes to secondary sites is likely to play an important role in the acquisition of new genes by bacterial and

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02232.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1995.tb02233.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY