Faculty Opinions recommendation of A Burkholderia thailandensis Acyl-Homoserine Lactone-Independent Orphan LuxR Homolog That Activates Production of the Cytotoxin Malleilactone.

2017 ◽  
Author(s):  
David Newman
Keyword(s):  
Homoserine Lactone ◽  
Acyl Homoserine Lactone ◽  
Burkholderia Thailandensis ◽  
Luxr Homolog

scholarly journals A Burkholderia thailandensis Acyl-Homoserine Lactone-Independent Orphan LuxR Homolog That Activates Production of the Cytotoxin Malleilactone

2015 ◽  
Vol 197 (21) ◽  
pp. 3456-3462 ◽  
Author(s):  
Thao T. Truong ◽  
Mohammad Seyedsayamdost ◽  
E. Peter Greenberg ◽  
Josephine R. Chandler
Keyword(s):  
Transcription Factors ◽  
Quorum Sensing ◽  
Gene Cluster ◽  
Homoserine Lactone ◽  
Acyl Homoserine Lactone ◽  
Burkholderia Thailandensis ◽  
Content Type ◽  
Laboratory Conditions ◽  
Luxr Homolog ◽  
Normal Laboratory

ABSTRACTBurkholderia thailandensishas three acyl-homoserine lactone (AHL) LuxR-LuxI quorum-sensing circuits and two orphan LuxR homologs. Orphans are LuxR-type transcription factors that do not have cognate LuxI-type AHL synthases. One of the orphans, MalR, is genetically linked to themalgene cluster, which encodes enzymes required for production of the cytotoxic polyketide malleilactone. Under normal laboratory conditions themalgene cluster is silent; however, antibiotics like trimethoprim inducemaltranscription. We show that trimethoprim-dependent induction of themalgenes requires MalR. MalR has all of the conserved amino acid residues characteristic of AHL-responsive LuxR homologs, but inB. thailandensis, MalR activation of malleilactone synthesis genes is not responsive to AHLs. MalR can activate transcription from themalpromoter inE. coliwithout addition of AHLs or trimethoprim. Expression ofmalRinB. thailandensisis induced by trimethoprim. Our data indicate that MalR binds to aluxbox-like element in themalpromoter and activates transcription of themalgenes in an AHL-independent manner. Antibiotics like trimethoprim appear to activatemalgene expression indirectly by somehow activatingmalRexpression. MalR activation of themalgenes represents an example of a LuxR homolog that is not a receptor for an AHL quorum-sensing signal. Our evidence is consistent with the idea thatmalgene activation depends solely on sufficient transcription of themalRgene.IMPORTANCELuxR proteins are transcription factors that are typically activated by acyl-homoserine lactone (AHL) signals. We demonstrate that a conserved LuxR family protein, MalR, activates genes independently of AHLs. MalR is required for transcription of genes coding for synthesis of the cytotoxic polyketide malleilactone. These genes are not expressed when cells are grown under normal laboratory conditions. In laboratory culture, MalR induction of malleilactone requires certain antibiotics, such as trimethoprim, which increasemalRexpression by an unknown mechanism. At sufficient levels ofmalRexpression, MalR functions independently of any external signal. Our findings show that MalR is an activator of the silent malleilactone biosynthesis genes and that MalR functions independently of AHLs.

scholarly journals Reversible Acyl-Homoserine Lactone Binding to Purified Vibrio fischeri LuxR Protein

2004 ◽  
Vol 186 (3) ◽  
pp. 631-637 ◽  
Author(s):  
M. L. Urbanowski ◽  
C. P. Lostroh ◽  
E. P. Greenberg
Keyword(s):  
Quorum Sensing ◽  
Promoter Region ◽  
Vibrio Fischeri ◽  
Homoserine Lactone ◽  
Acyl Homoserine Lactone ◽  
E Coli ◽  
High Affinity ◽  
Founding Member ◽  
Luxr Homolog

ABSTRACT The Vibrio fischeri LuxR protein is the founding member of a family of acyl-homoserine lactone-responsive quorum-sensing transcription factors. Previous genetic evidence indicates that in the presence of its quorum-sensing signal, N-(3-oxohexanoyl) homoserine lactone (3OC6-HSL), LuxR binds to lux box DNA within the promoter region of the luxI gene and activates transcription of the luxICDABEG luminescence operon. We have purified LuxR from recombinant Escherichia coli. Purified LuxR binds specifically and with high affinity to DNA containing a lux box. This binding requires addition of 3OC6-HSL to the assay reactions, presumably forming a LuxR-3OC6-HSL complex. When bound to the lux box at the luxI promoter in vitro, LuxR-3OC6-HSL enables E. coli RNA polymerase to initiate transcription from the luxI promoter. Unlike the well-characterized LuxR homolog TraR in complex with its signal (3-oxo-octanoyl-HSL), the LuxR-30C6-HSL complex can be reversibly inactivated by dilution, suggesting that 3OC6-HSL in the complex is not tightly bound and is in equilibrium with the bulk solvent. Thus, although LuxR and TraR both bind 3-oxoacyl-HSLs, the binding is qualitatively different. The differences have implications for the ways in which these proteins respond to decreases in signal concentrations or rapid drops in population density.

scholarly journals A Burkholderia cenocepacia Orphan LuxR Homolog Is Involved in Quorum-Sensing Regulation

2009 ◽  
Vol 191 (8) ◽  
pp. 2447-2460 ◽  
Author(s):  
Rebecca J. Malott ◽  
Eoin P. O'Grady ◽  
Jessica Toller ◽  
Silja Inhülsen ◽  
Leo Eberl ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Negative Regulation ◽  
Burkholderia Cenocepacia ◽  
Acyl Homoserine Lactone ◽  
Independent Manner ◽  
Reverse Transcription Pcr ◽  
Luxr Homolog ◽  
Genes Encoding

ABSTRACT Burkholderia cenocepacia utilizes quorum sensing to control gene expression, including the expression of genes involved in virulence. In addition to CepR and CciR, a third LuxR homolog, CepR2, was found to regulate gene expression and virulence factor production. All B. cenocepacia strains examined contained this orphan LuxR homolog, which was not associated with an adjacent N-acyl-homoserine lactone synthase gene. Expression of cepR2 was negatively autoregulated and was negatively regulated by CciR in strain K56-2. Microarray analysis and quantitative reverse transcription-PCR determined that CepR2 did not influence expression of cepIR or cciIR. However, in strain K56-2, CepR2 negatively regulated expression of several known quorum-sensing-controlled genes, including genes encoding zinc metalloproteases. CepR2 exerted positive and negative regulation on genes on three chromosomes, including strong negative regulation of a gene cluster located adjacent to cepR2. In strain H111, which lacks the CciIR quorum-sensing system, CepR2 positively regulated pyochelin production by controlling transcription of one of the operons required for the biosynthesis of the siderophore in an N-acyl-homoserine lactone-independent manner. CepR2 activation of a luxI promoter was demonstrated in a heterologous Escherichia coli host, providing further evidence that CepR2 can function in the absence of signaling molecules. This study demonstrates that the orphan LuxR homolog CepR2 contributes to the quorum-sensing regulatory network in two distinct strains of B. cenocepacia.

scholarly journals AnN-Acyl Homoserine Lactone Synthase in the Ammonia-Oxidizing Bacterium Nitrosospira multiformis

2013 ◽  
Vol 80 (3) ◽  
pp. 951-958 ◽  
Author(s):  
Jie Gao ◽  
Anzhou Ma ◽  
Xuliang Zhuang ◽  
Guoqiang Zhuang
Keyword(s):  
Regulatory Networks ◽  
Homoserine Lactone ◽  
Great Sensitivity ◽  
Acyl Homoserine Lactone ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Luxr Homolog ◽  
Ammonia Oxidizing Bacterium ◽  
Culture Supernatants ◽  
Long Chain

ABSTRACTThe chemolithoautotrophic bacteriumNitrosospira multiformisis involved in affecting the process of nitrogen cycling. Here we report the existence and characterization of a functional quorum sensing signal synthase inN. multiformis. One gene (nmuI) playing a role in generating a protein with high levels of similarity toN-acyl homoserine lactone (AHL) synthase protein families was identified. Two AHLs (C14-AHL and 3-oxo-C14-AHL) were detected using an AHL biosensor and liquid chromatography-mass spectrometry (LC-MS) whennmuI, producing a LuxI homologue, was introduced intoEscherichia coli. However, by extractingN. multiformisculture supernatants with acidified ethyl acetate, no AHL product was obtained that was capable of activating the biosensor or being detected by LC-MS. According to reverse transcription-PCR, thenmuIgene is transcribed inN. multiformis, and a LuxR homolog (NmuR) in this ammonia-oxidizing strain showed great sensitivity to long-chain AHL signals by solubility assay. A degradation experiment demonstrated that the absence of AHL signals might be attributed to the possible AHL-inactivating activities of this strain. To summarize, an AHL synthase gene (nmuI) acting as a long-chain AHL producer has been found in a chemolithotrophic ammonia-oxidizing microorganism, and the results provide an opportunity to complete the knowledge of the regulatory networks inN. multiformis.

scholarly journals Discovery of Pandoraea pnomenusa RB38 N-acyl homoserine Lactone Synthase (PpnI) and its Complete Genome Sequence Analysis

2015 ◽  
Author(s):  
Kok-Gan Chan ◽  
Robson Ee ◽  
Kah-Yan How ◽  
Siew-Kim Lee ◽  
Wai-Fong Yin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Homoserine Lactone ◽  
Tandem Mass ◽  
Acyl Homoserine Lactone ◽  
Multiple Sequence ◽  
Genome Sequence Analysis ◽  
Luxr Homolog ◽  
Distinct Cluster ◽  
Complete Genome Sequence Analysis ◽  
Phylogenetic Neighbor

In this study, we sequenced the genome of P. pnomenusa RB38 and reported the finding of a pair of cognate luxI/R homologs which we firstly coined as ppnI, which is found adjacent to a luxR homolog, ppnR. An additional orphan luxR homolog, ppnR2 was also discovered. Multiple sequence alignment revealed that PpnI is a distinct cluster of AHL synthase compared to those of its nearest phylogenetic neighbor, Burkholderia spp. When expressed heterologously and analysed using high resolution tandem mass spectrometry, PpnI directs the synthesis of N-octanoylhomoserine lactone (C8-HSL). To our knowledge, this is the first documentation of the luxI/R homologs of the genus of Pandoraea.

scholarly journals A single point mutation converts a glutaryl-7-aminocephalosporanic acid acylase into an N-acyl-homoserine lactone acylase

2021 ◽  
Author(s):  
Shereen A. Murugayah ◽  
Gary B. Evans ◽  
Joel D. A. Tyndall ◽  
Monica L. Gerth
Keyword(s):  
Single Point ◽  
Quorum Quenching ◽  
Homoserine Lactone ◽  
Site Directed Mutagenesis ◽  
Saturation Mutagenesis ◽  
Single Amino Acid ◽  
Single Point Mutation ◽  
Acyl Homoserine Lactone ◽  
Signalling Molecules ◽  
Single Amino Acid Residue

Abstract Objective To change the specificity of a glutaryl-7-aminocephalosporanic acid acylase (GCA) towards N-acyl homoserine lactones (AHLs; quorum sensing signalling molecules) by site-directed mutagenesis. Results Seven residues were identified by analysis of existing crystal structures as potential determinants of substrate specificity. Site-saturation mutagenesis libraries were created for each of the seven selected positions. High-throughput activity screening of each library identified two variants—Arg255Ala, Arg255Gly—with new activities towards N-acyl homoserine lactone substrates. Structural modelling of the Arg255Gly mutation suggests that the smaller side-chain of glycine (as compared to arginine in the wild-type enzyme) avoids a key clash with the acyl group of the N-acyl homoserine lactone substrate. Conclusions Mutation of a single amino acid residue successfully converted a GCA (with no detectable activity against AHLs) into an AHL acylase. This approach may be useful for further engineering of ‘quorum quenching’ enzymes.

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