DNA-protein recognition: demonstration of three genetically separated operator elements that are required for repression of the Escherichia coli deoCABD promoters by the DeoR repressor.

Valentin‐Hansen, Poul; Albrechtsen, Bjarne; Larsen, Jens Erik Løve

doi:10.1002/j.1460-2075.1986.tb04458.x

Cited by 106 publications

(71 citation statements)

References 26 publications

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“…chrysanthemi and E. coli derivatives are listed in Table 1. Plasmids used for subcloning experiments were pJEL250 (Valentin-Hansen et al, 1986), pBR328 (Soberon et al, 1980) and pKO3 (Link et al, 1997). Plasmid pN496 was a pBluescript derivative from the laboratory collection, containing a uidA-kan cassette flanked by multiple cloning sites.…”

Section: Methodsmentioning

confidence: 99%

Tol-Pal proteins are critical cell envelope components of Erwinia chrysanthemi affecting cell morphology and virulence

Dubuisson

Vianney

Hugouvieux‐Cotte‐Pattat

et al. 2005

Microbiology

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The tol-pal genes are necessary for maintaining the outer-membrane integrity of Gram-negative bacteria. These genes were first described in Escherichia coli, and more recently in several other species. They are involved in the pathogenesis of E. coli, Haemophilus ducreyi, Vibrio cholerae and Salmonella enterica. The role of the tol-pal genes in bacterial pathogenesis was investigated in the phytopathogenic enterobacterium Erwinia chrysanthemi, assuming that this organism might be a good model for such a study. The whole Er. chrysanthemi tol-pal region was characterized. Tol-Pal proteins, except TolA, showed high identity scores with their E. coli homologues. Er. chrysanthemi mutants were constructed by introducing a uidA-kan cassette in the ybgC, tolQ, tolA, tolB, pal and ybgF genes. All the mutants were hypersensitive to bile salts. Mutations in tolQ, tolA, tolB and pal were deleterious for the bacteria, which required high concentrations of sugars or osmoprotectants for their viability. Consistent with this observation, they were greatly impaired in their cell morphology and division, which was evidenced by observations of cell filaments, spherical forms, membrane blebbing and mislocalized bacterial septa. Moreover, tol-pal mutants showed a reduced virulence in a potato tuber model and on chicory leaves. This could be explained by a combination of impaired phenotypes in the tol-pal mutants, such as reduced growth and motility and a decreased production of pectate lyases, the major virulence factor of Er. chrysanthemi. INTRODUCTIONThe Tol-Pal system of Gram-negative bacteria is required for outer-membrane stability (Lazzaroni et al., 1999). It comprises five envelope proteins, TolQ, TolR, TolA, TolB and Pal, which form two complexes. The TolQ, TolR and TolA inner-membrane proteins interact via their transmembrane domains (Derouiche et al., 1995;Lazzaroni et al., 1995). The b-propeller domain of the periplasmic protein TolB is responsible for its interaction with Pal (Ray et al., 2000). TolB also interacts with the outer-membrane peptidoglycan-associated proteins Lpp and OmpA (Cascales et al., 2002;Clavel et al., 1998). TolA undergoes a conformational change in response to changes in the protonmotive force (Germon et al., 2001), and interacts with Pal in an energy-dependent manner (Cascales et al., 2001). The Cterminal periplasmic domain of TolA also interacts with the N-terminal domain of TolB (Dubuisson et al., 2002;Walburger et al., 2002).The transcriptional organization of the E. coli tol-pal genes has been characterized. The genes ybgC (orf1), tolQ, tolR, tolA and tolB, and pal and ybgF (orf2) form two operons (Muller & Webster, 1997); a large ybgC-ybgF transcript has also been postulated (Vianney et al., 1996). ybgC and ybgF encode proteins of unknown function located in the cytoplasm and the periplasm, respectively (Clavel et al., 1996;Sun & Webster, 1987). Inactivation of these two ORFs induces no obvious phenotype in E. coli. In contrast, mutations in the tol-pal genes cause the disruption of outermembr...

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Section: Methodsmentioning

confidence: 99%

Tol-Pal proteins are critical cell envelope components of Erwinia chrysanthemi affecting cell morphology and virulence

Dubuisson

Vianney

Hugouvieux‐Cotte‐Pattat

et al. 2005

Microbiology

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“…However, more complex modes of regulation involving multipartite operators are demanded for the bacterial gal operon, and for the ara (Dunn et al 1984) and deo operons (Valentin-Hansen et al 1986). As noted above, even the paradigm lac operon m a y use a second operator site for full repression.…”

Section: Transcriptional Control By Association Of Dna-bound Regulatomentioning

confidence: 99%

DNA looping in cellular repression of transcription of the galactose operon.

Mandal¹,

Su²,

Haber³

et al. 1990

Genes Dev.

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Communication between distant DNA sites is a central feature of many DNA transactions. Negative regulation of the galactose (ga/) operon of Escherichia coli requires repressor binding to two operator sites located on opposite sides of the promoter. The proposed mechanism for regulation involves binding of the repressor to both operator sites, followed by a protein-protein association that loops the intervening promoter DNA (double occupancy plus association). To assess these requirements in vivo, we have previously converted ga/operator sites to lac and shown that both operator sites must be occupied by the homologous repressor protein (Lac or Gal) for negative regulation of the ga/operon. We have now addressed more directly the need for proteinprotein association by the use of the converted operator sites and a mutant Lac repressor defective in association of the DNA-binding dimers. We have compared the biological and biochemical activity of two Lac repressors: the wild-type (tetramer) I + form, in which the DNA-binding dimer units are tightly associated; and the mutant I "~ repressor, in which the dimer units do not associate effectively. The I ÷ repressor is an efficient negative regulator of the ga/operon in vivo, but the I "~ mutant is an ineffective repressor. Purified I + repressor efficiently forms DNA loops between operator sites that we have visualized by electron microscopy; the I °~ repressor fails to form DNA loops, although the protein binds effectively to both operator sites. From the clear correlation between looping in vitro and repression in vivo, we conclude that regulation of the ga/operon depends on the association of repressor proteins bound to the two operator sites. Repression is likely to involve a DNA-wound nucleoprotein complex in which RNA polymerase is present but unable to carry out a productive interaction with the promoter sequence.

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“…We propose that this looping of the DNA resulting from Hin tetramer formation plays a role in the switching bias. Long-range protein-protein interactions have been shown to be involved in regulation of the ara, deo, gal, and lac operons of E. coli (9,11,14,15,20,48). In vivo binding of Hin to a defective hix site is enhanced by the presence of another functional hix site even at a distance of 1 kb (16a), suggesting a role of tetramer formation in binding.…”

mentioning

confidence: 99%

Negative regulatory loci coupling flagellin synthesis to flagellar assembly in Salmonella typhimurium

1991

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The complex regulation of flagellin gene expression in Salmonella typhimurium was characterized in vivo by using lac transcriptional fusions to the two flagellin structural genes (fliC [Hl] andfljB [H2]). Phase variation was measured as the rate of switching of flagellin gene expression. Switching frequencies varied from 1/500 per cell per generation to 1/10,000 per cell per generation depending on the particular insertion and the direction of switching. There is a 4-to 20-fold bias in favor of switching from thefljB(On) to thefljB(Of) orientation. Random TnlOdTc insertions were isolated which failed to express flagellin. While most of these insertions mapped to loci known to be required for flagellin expression, several new loci were identified. The presence of functional copies of all of the genes responsible for complete flagellar assembly, except the hook-associated proteins (flgK,flgL, andfliD gene products), were required for expression of thefliC orfljB flagellin genes. Two novel loci involved in negative regulation offliC andfljB infla mutant backgrounds were identified. One of these loci, designated the flgR locus, mapped to the flg operon at 23 min on the Salmonella linkage map. An flgR insertion mutation resulted in relief of repression of thefliC andfljB genes in allfla mutant backgrounds except for mutants in the positive regulatory loci (flhC, flhD, and fli4 genes).Flagellar phase variation in Salmonella typhimurium results from the reversible inversion of a 996-bp chromosomal segment of DNA ( rium and with the homologous genes in Escherichia coli has uncovered a complex hierarchy of regulation for these genes (26,31,32,53). In S. typhimurium one and presumably also the other of the flagellin genes are at the bottom of this regulatory scheme and are grouped in the class of late genes (Fig. 2) (32). The members of this class are dependent on the early and middle gene classes for their expression. If any of the genes in the early and middle classes do not express functional proteins, the genes in the late class are not expressed.Similarly, the genes in the middle class are dependent upon the early class for their expression but are regulated independently of any defects in the late genes (32). The early genes include the flhD and flhC genes, which are believed to encode positive activators of flagellar expression (29). These early genes are required for expression of the middle genes.The fliA gene, shown recently to encode a flagellar-specific sigma factor (38), is included among the middle genes. The fliA gene product is thought to be required for the expression of the late genes, including flagellin.At the top of this regulatory scheme is the cAMP-Catabolite gene activator protein complex, which acts at the early genes (flhDC operon) (29, 42). In cya or crp mutant strains or in wild-type cells grown in the presence of glucose, no flagella are synthesized (1, 54). These proposed classes or levels of regulation of flagellar assembly in S. typhimurium are similar to those proposed for E. coli by Kome...

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DNA-protein recognition: demonstration of three genetically separated operator elements that are required for repression of the Escherichia coli deoCABD promoters by the DeoR repressor.

Cited by 106 publications

References 26 publications

Tol-Pal proteins are critical cell envelope components of Erwinia chrysanthemi affecting cell morphology and virulence

Tol-Pal proteins are critical cell envelope components of Erwinia chrysanthemi affecting cell morphology and virulence

DNA looping in cellular repression of transcription of the galactose operon.

Negative regulatory loci coupling flagellin synthesis to flagellar assembly in Salmonella typhimurium

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