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Query: UNIPROT:P06889 (Mol)
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Yersinia enterocolitica produces compounds capable of transcriptionally activating the Photobacterium fischeri bioluminescence (lux) operon. Using high-performance liquid chromatography, high resolution tandem mass spectrometry in conjunction with chemical synthesis, two signal molecules were identified and shown to be N-hexanoyl-L-homoserine lactone (HHL) and N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). A gene (yenI) was isolated from Y. enterocolitica and demonstrated to direct the synthesis of both HHL and OHHL. DNA sequence analysis revealed an open reading frame (ORF) of 642 bp encoding a protein (YenI) of 24.6 kDa with approximately 20% identity to the LuxI family of proteins. Northern blot analysis of yenI expression indicated yenI is transcribed as a single gene and 5' transcript mapping of yenI identified a transcriptional start site 89 bp upstream of the ORF. DNA sequence analysis of the region downstream of yenI located a second ORF, termed yenR, with significant homology to the LuxR family of transcriptional activators. An insertion mutation of yenI abolishes HHL and OHHL production, indicating its central role in N-acylhomoserine lactone synthesis in Y. enterocolitica. Transcriptional analysis using a chromosomal yenI::luxAB fusion has demonstrated that yenI is not subject to autoinduction but is expressed constitutively. Whilst production of the Yop proteins in the wild type and in yenI mutants is indistinguishable, two-dimensional SDS-PAGE analysis of total cell proteins indicated that a number of proteins lack the yenI mutant.
Mol Microbiol 1995 Jul
PMID:Characterisation of the yenI/yenR locus from Yersinia enterocolitica mediating the synthesis of two N-acylhomoserine lactone signal molecules. 749 83

The LuxR regulatory protein of Vibrio harveyi as well as the autoinducer molecule, N-(3-hydroxybutanoyl) homoserine lactone, are known to be required for expression of luminescence. Although LuxR has been implicated in the activation of the promoter of the lux operon of V. harveyi, and can bind to two distinct sites upstream of the transcription initiation start site, its mode of action is unknown. In the present experiments, mobility shift assays were used to demonstrate that LuxR bound to the distal and proximal sites in an independent rather than co-operative interaction with a much tighter binding to the distal site. Deletion mutation analyses of DNA upstream of the lux promoter followed by transconjugation into V. harveyi in trans using the chloramphenicol acetyltransferase (cat) gene as a reporter demonstrated, however, that the proximal site for LuxR was absolutely critical for promoter activation while the distal LuxR site was only necessary for maximum activation. This result was confirmed by mutation of the proximal site which blocked activation of the lux promoter and binding of LuxR to this site, but did not prevent LuxR binding to the distal site.
Mol Microbiol 1994 Oct
PMID:Proximal and distal sites bind LuxR independently and activate expression of the Vibrio harveyi lux operon. 783 May 70

The pheromone N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) regulates expression of bioluminescence in the marine bacterium Vibrio fischeri, the production of carbapenem antibiotic in Erwinia carotovora and exoenzymes in both E. carotovora and Pseudomonas aeruginosa. A characteristic feature of this regulatory mechanism in V. fischeri is that it is cell density-dependent, reflecting the need to accumulate sufficient pheromone to trigger the induction of gene expression. Using a lux plasmid-based bioluminescent sensor for OHHL, pheromone production by E. carotovora, Enterobacter agglomerans, Hafnia alvei, Rahnella aquatilis and Serratia marcescens has been demonstrated and shown also to be cell density-dependent. Production of OHHL implies the presence in these bacteria of a gene equivalent to luxI. Chromosomal banks from all five enteric bacteria have yielded clones capable of eliciting OHHL production when expressed in Escherichia coli. The luxI homologue from both E. carotovora (carI) and E. agglomerans (eagI) were characterized at the DNA sequence level and the deduced protein sequences have only 25% identity with the V. fischeri LuxI. Despite this, carI, eagI and luxI are shown to be biologically equivalent. An insertion mutant of eagI demonstrates that this gene is essential for OHHL production in E. agglomerans.
Mol Microbiol 1993 Nov
PMID:A novel strategy for the isolation of luxI homologues: evidence for the widespread distribution of a LuxR:LuxI superfamily in enteric bacteria. 796 29

Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. One signal-response system is encoded by the luxL,M,N locus. The luxL and luxM genes are required for the production of an autoinducer (probably beta-hydroxybutyl homoserine lactone), and the luxN gene is required for the response to that autoinducer. Analysis of the phenotypes of LuxL,M and N mutants indicated that an additional signal-response system also controls density sensing. We report here the identification, cloning and analysis of luxP and luxQ, which encode functions required for a second density-sensing system. Mutants with defects in luxP and luxQ are defective in response to a second autoinducer substance. LuxQ, like LuxN, is similar to members of the family of two-component, signal transduction proteins and contains both a histidine protein kinase and a response regulator domain. Analysis of signalling mutant phenotypes indicates that there are at least two separate signal-response pathways which converge to regulate expression of luminescence in V. harveyi.
Mol Microbiol 1994 Jul
PMID:Multiple signalling systems controlling expression of luminescence in Vibrio harveyi: sequence and function of genes encoding a second sensory pathway. 798 7

We have utilized a gene from bacteriophage T3 that encodes the enzyme S-adenosylmethionine hydrolase (SAMase) to generate transgenic tomato plants that produce fruit with a reduced capacity to synthesize ethylene. S-adenosylmethionine (SAM) is the metabolic precursor of 1-aminocyclopropane-1-carboxylic acid, the proximal precursor to ethylene. SAMase catalyzes the conversion of SAM to methylthioadenosine and homoserine. To restrict the presence of SAMase to ripening fruit, the promoter from the tomato E8 gene was used to regulate SAMase gene expression. Transgenic tomato plants containing the 1.1 kb E8 promoter bore fruit that expressed SAMase during the breaker and orange stage of fruit ripening and stopped expression after the fruit fully ripened. Plants containing the 2.3 kb E8 promoter expressed SAMase at higher levels during the post-breaker phases of fruit ripening and had a substantially reduced capacity to synthesize ethylene.
Plant Mol Biol 1994 Nov
PMID:Reduced ethylene synthesis by transgenic tomatoes expressing S-adenosylmethionine hydrolase. 799 94

Conjugation of Agrobacterium tumefaciens wide-host-range octopine-type Ti plasmids is regulated by the LuxR-type transcriptional activator TraR in conjunction with an acylated homoserine lactone designated AAI. Expression of traR in octopine-type Ti plasmids is stimulated by OccR in response to octopine, an opine released from crown gall tumours, and is also positively autoregulated by TraR and AAI. Genetic and physical mapping of these promoters indicates that the OccR-activated promoter lies 14.5 kb upstream of traR, while the TraR-activated promoter lies 6 kb upstream. The upstream portion of the 14.5 kb operon contains seven previously characterized genes that direct the uptake and catabolism of octopine. The TraR-activated promoter lies just downstream from the octopine catabolic genes, and transcribes six genes in addition to traR, including five genes (ophABCDE) that show strong homology to oligo-peptide permeases of Salmonella typhimurium and Bacillus subtilis. Several TraR-regulated promoters overlap with 18 bp inverted repeats called tra boxes. In contrast, the traR autoregulatory promoter is not associated with a consensus tra box.
Mol Microbiol 1996 Jun
PMID:Localization of OccR-activated and TraR-activated promoters that express two ABC-type permeases and the traR gene of Ti plasmid pTiR10. 880 72

Erwinia carotovora subsp. carotovora wild-type strain Ecc71 does not elicit the hypersensitive reaction (HR) in tobacco leaves. By mini-Tn5-Km and chemical mutagenesis we have isolated RsmA- mutants of Ecc71 that produce high basal levels of pectate lyases, polygalacturonase, cellulase, and protease; they also are hypervirulent. The RsmA- mutants, but not their parent strains, elicit an HR-like response in tobacco leaves. This reaction is characterized by the rapid appearance of water soaking followed by tissue collapse and necrosis. The affected areas remain limited to the region infiltrated with bacterial cells, and the symptoms closely resemble a typical HR, e.g., the reactions caused by Pseudomonas syringae pv. pisi. Moreover, low concentrations of cells of the mini-Tn5-Km insertion RsmA- mutant, AC5070, infiltrated into tobacco leaf tissue prevent elicitation of the rapid necrosis by AC5070 or by P. syringae pv. pisi. Elicitation of the HR-like response by the mutants is not affected by the deficiency of N-(3-oxohexanoyl)-L-homoserine lactone, the cell density (quorum) sensing signal. Cloning and sequence analysis have disclosed that E. carotovora subsp. carotovora strain Ecc71 possesses a homolog of E. chrysanthemi hrpN known to encode an elicitor of the HR; the corresponding Ecc71 gene is designated hrpNEcc. Northern (RNA) blot data show that the level of hrpNEcc mRNA is considerably higher in the RsmA- mutants than in the RsmA+ strains. Moreover, a low copy plasmid carrying the rsmA+ allele severely reduces the level of the hrpNEcc transcripts in the RsmA- mutants. These constructs, like the RsmA+ E. carotovora subsp. carotovora strains, do not elicit the HR-like response. These data taken along with the effects of rsmA on exoenzyme production and pathogenicity (A. Chatterjee et al., 1995, Appl. Environ. Microbiol. 61:1959-1967) demonstrate that this global regulator gene plays a critical role in plant interaction of E. carotovora subsp. carotovora.
Mol Plant Microbe Interact 1996 Sep
PMID:The RsmA- mutants of Erwinia carotovora subsp. carotovora strain Ecc71 overexpress hrpNEcc and elicit a hypersensitive reaction-like response in tobacco leaves. 881 71

Several bacterial species possess the ability to differentiate into highly motile swarmer cells capable of rapid surface colonization. In Serratia liquefaciens, we demonstrate that initiation of swarmer-cell differentiation involves diffusible signal molecules that are released into the growth medium. Using high-performance liquid chromatography (HPLC), high resolution mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, we identified N-butanoyl-L-homoserine lactone (BHL) and N-hex anoyl-L-homoserine lactone (HHL) in cell-free Serratia culture supernatants. BHL and HHL are present in a ratio of approximately 10:1 and their structures were unequivocally confirmed by chemical synthesis. The swrl (swarmer initiation) gene, the predicted translation product of which exhibits substantial homology to the LuxI family of putative N-acyl homoserine lactone (AHL) synthases is responsible for directing synthesis of both BHL and HHL. In an swrl mutant, swarming motility is abolished but can be restored by the addition of an exogenous AHL. These results add swarming motility to the rapidly expanding list of phenotypes known to be controlled through quorum sensing.
Mol Microbiol 1996 Apr
PMID:Involvement of N-acyl-L-hormoserine lactone autoinducers in controlling the multicellular behaviour of Serratia liquefaciens. 886 Dec 11

In Pseudomonas aeruginosa, the production of many virulence factors and secondary metabolites is regulated in concert with cell density through quorum sensing. Two quorum-sensing regulons have been identified in which the LuxR homologues LasR and RhlR are activated by N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) and N-butanoyl-L-homoserine lactone (BHL) respectively. The lasR and rhlR genes are linked to the luxl homologues lasl and rhll, which are responsible for synthesis of OdDHL and BHL, respectively. As lasRl and rhlRl are both involved in regulating synthesis of exoenzymes such as elastase, we sought to determine the nature of their interrelationship. By using lacZ transcriptional fusions in both homologous (P. aeruginosa) and heterologous (Escherichia coli) genetic backgrounds we provide evidence that (i) lasR is expressed constitutively throughout the growth cycle, (ii) rhlR expression is regulated by LasR/OdDHL, and (iii) that RhlR/BHL regulates rhll. We also show that expression of the stationary-phase sigma factor gene rpoS is abolished in a P. aeruginosa lasR mutant and in the pleiotropic BHL-negative mutant PANO67. Furthermore, our data reveal that kin E. coli, an rpoS-lacZ fusion is regulated directly by RhlR/BHL. Taken together, these results indicate that P. aeruginosa employs a multilayered hierarchical quorum-sensing cascade involving RhlR/BHL and LasR/OdDHL, interlinked via RpoS, to integrate the regulation of virulence determinants and secondary metabolites with adaptation and survival in the stationary phase.
Mol Microbiol 1996 Sep
PMID:A hierarchical quorum-sensing cascade in Pseudomonas aeruginosa links the transcriptional activators LasR and RhIR (VsmR) to expression of the stationary-phase sigma factor RpoS. 889 83

Eel calcitonin (CT) analogues having C-terminal homoserine (Hse)-amide at position 31, 32, or 33 were synthesized, and in vivo hypocalcemic activity of the analogues were determined. The present study showed that: (i) An eel CT analogue having Hse-amide at position 32 was more active than native eel CT, and the duration of hypocalcemic action of the analogue was equivalent to that of native eel CT. (ii) Either curtailment or elongation of [Hse32-amide]-eel CT peptide chain by one amino acid resulted in a great loss of hypocalcemic activity. The results of the present study indicate that Pro-amide at the C-terminus of CT is not essential for its biological activity in vivo. Replacement of C-terminal Pro32-amide by Hse32-amide in eel CT molecule produced an analogue with a hypocalcemic activity greater than that of native eel CT.
Biochem Mol Biol Int 1996 Nov
PMID:A novel biologically active eel calcitonin analogue with carboxyl terminal Hse32-amide: carboxyl terminal Pro32-amide in calcitonin is not essential for biological activity. 895 81


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