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de Las Heras A, Martínez-García E, Domingo-Sananes MR, Fraile S, de Lorenzo V. Rationally rewiring the connectivity of the XylR/Pu regulatory node of the m-xylene degradation pathway in Pseudomonas putida. Integr Biol (Camb) 2016; 8:571-6. [PMID: 26961967 DOI: 10.1039/c5ib00310e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The XylR/Pu regulatory node of the m-xylene biodegradation pathway of Pseudomonas putida mt-2 is one of the most intricate cases of processing internal and external cues into a single controlling element. Despite this complexity, the performance of the regulatory system is determined in vivo only by the occupation of Pu by m-xylene-activated XylR and σ(54)-RNAP. The stoichiometry between these three elements defines natural system boundaries that outline a specific functional space. This space can be expanded artificially following different strategies that involve either the increase of XylR or σ(54) or both elements at the same time (each using a different inducer). In this work we have designed a new regulatory architecture that drives the system to reach a maximum performance in response to one single input. To this end, we first explored using a simple mathematical model whether the output of the XylR/Pu node could be amended by simultaneously increasing σ(54) and XylR in response to only natural inducers. The exacerbation of Pu activity in vivo was tested in strains bearing synthetic transposons encoding xylR and rpoN (the σ(54) coding gene) controlled also by Pu, thereby generating a P. putida strain with the XylR/Pu output controlled by two intertwined feed forward loops (FFLs). The lack of a negative feedback loop in the expression node enables Pu activity to reach its physiological maximum in response to a single input. Only competition for cell resources might ultimately check the upper activity limit of such a rewired m-xylene sensing device.
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Affiliation(s)
- Aitor de Las Heras
- Systems Biology Program, Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049, Spain.
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Transcription factor levels enable metabolic diversification of single cells of environmental bacteria. ISME JOURNAL 2015; 10:1122-33. [PMID: 26636554 DOI: 10.1038/ismej.2015.193] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/27/2015] [Accepted: 09/22/2015] [Indexed: 12/19/2022]
Abstract
Transcriptional noise is a necessary consequence of the molecular events that drive gene expression in prokaryotes. However, some environmental microorganisms that inhabit polluted sites, for example, the m-xylene degrading soil bacterium Pseudomonas putida mt-2 seem to have co-opted evolutionarily such a noise for deploying a metabolic diversification strategy that allows a cautious exploration of new chemical landscapes. We have examined this phenomenon under the light of deterministic and stochastic models for activation of the main promoter of the master m-xylene responsive promoter of the system (Pu) by its cognate transcriptional factor (XylR). These analyses consider the role of co-factors for Pu activation and determinants of xylR mRNA translation. The model traces the onset and eventual disappearance of the bimodal distribution of Pu activity along time to the growth-phase dependent abundance of XylR itself, that is, very low in exponentially growing cells and high in stationary. This tenet was validated by examining the behaviour of a Pu-GFP fusion in a P. putida strain in which xylR expression was engineered under the control of an IPTG-inducible system. This work shows how a relatively simple regulatory scenario (for example, growth-phase dependent expression of a limiting transcription factor) originates a regime of phenotypic diversity likely to be advantageous in competitive environmental settings.
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de las Heras A, Martínez-García E, Domingo-Sananes MR, de Lorenzo V. Widening functional boundaries of the σ(54) promoter Pu of Pseudomonas putida by defeating extant physiological constraints. MOLECULAR BIOSYSTEMS 2015; 11:734-42. [PMID: 25560994 DOI: 10.1039/c4mb00557k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The extant layout of the σ(54) promoter Pu, harboured by the catabolic TOL plasmid, pWW0, of Pseudomonas putida is one of the most complex instances of endogenous and exogenous signal integration known in the prokaryotic domain. In this regulatory system, all signal inputs are eventually translated into occupation of the promoter sequence by either of two necessary components: the m-xylene responsive transcriptional factor XylR and the σ(54) containing form of RNA polymerase. Modelling of these components indicated that the Pu promoter could be upgraded to respond with much greater capacity to aromatic inducers by artificially increasing the endogenous levels of both XylR and the σ(54) sigma factor, either separately or together. To explore these scenarios, expression of rpoN, the gene encoding σ(54), was placed under the control of an orthogonal regulatory system that was inducible by salicylic acid. We generated a knock-in P. putida strain containing this construct alongside the xylR/Pu regulatory module in its native configuration, and furthermore, a second strain where xylR expression was under the control of an engineered positive-feedback loop. These interventions allowed us to dramatically increase the transcriptional capacity (i.e. absolute promoter output) of Pu far beyond its natural scope. In addition, they resulted in a new regulatory device displaying more sensitive and ultra-fast responses to m-xylene. To our knowledge, this is the first time that the working regime of a promoter has been rationally modified by releasing the constraints imposed by its innate constituents.
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Affiliation(s)
- Aitor de las Heras
- Systems Biology Program, Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049, Spain.
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Calles B, Lorenzo VD. Expanding the boolean logic of the prokaryotic transcription factor XylR by functionalization of permissive sites with a protease-target sequence. ACS Synth Biol 2013; 2:594-603. [PMID: 23875967 DOI: 10.1021/sb400050k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The σ54-dependent prokaryotic regulator XylR implements a one-input/one-output actuator that transduces the presence of the aromatic effector m-xylene into transcriptional activation of the cognate promoter Pu. Such a signal conversion involves the effector-mediated release of the intramolecular repression of the N-terminal A domain on the central C module of XylR. On this background, we set out to endow this regulator with additional signal-sensing capabilities by inserting a target site of the viral protease NIa in permissive protein locations that once cleaved in vivo could either terminate XylR activity or generate an effector-independent, constitutive transcription factor. To find optimal protein positions to this end, we saturated the xylR gene DNA with a synthetic transposable element designed for randomly delivering in-frame polypeptides throughout the sequence of any given protein. This Tn5-based system supplies the target gene with insertions of a selectable marker that can later be excised, leaving behind the desired (poly) peptides grafted into the protein structure. Implementation of such knock-in-leave-behind (KILB) method to XylR was instrumental to produce a number of variants of this transcription factor (TF) that could compute in vivo two inputs (m-xylene and protease) into a single output following a logic that was dependent on the site of the insertion of the NIa target sequence in the TF. Such NIa-sensitive XylR specimens afforded the design of novel regulatory nodes that entered protease expression as one of the signals recognized in vivo for controlling Pu. This approach is bound to facilitate the functionalization of TFs and other proteins with new traits, especially when their forward engineering is made difficult by, for example, the absence of structural data.
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Affiliation(s)
- Belen Calles
- Systems Biology Program, Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco,
28049 Madrid, Spain
| | - Víctor de Lorenzo
- Systems Biology Program, Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco,
28049 Madrid, Spain
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Fraile S, Jiménez JI, Gutiérrez C, de Lorenzo V. NanoPad: An integrated platform for bacterial production of camel nanobodies aimed at detecting environmental biomarkers. Proteomics 2013; 13:2766-75. [DOI: 10.1002/pmic.201300009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 02/11/2013] [Accepted: 03/26/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Sofía Fraile
- Systems Biology Program; Centro Nacional de Biotecnología-CSIC; Campus de Cantoblanco; Madrid Spain
| | - Jose I. Jiménez
- Systems Biology Program; Centro Nacional de Biotecnología-CSIC; Campus de Cantoblanco; Madrid Spain
| | - Carlos Gutiérrez
- Department of Animal Pathology; Faculty of Veterinary Science; Las Palmas University; Canary Islands Spain
| | - Víctor de Lorenzo
- Systems Biology Program; Centro Nacional de Biotecnología-CSIC; Campus de Cantoblanco; Madrid Spain
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Silva-Rocha R, de Lorenzo V. The TOL network ofPseudomonas putidamt-2 processes multiple environmental inputs into a narrowresponse space. Environ Microbiol 2012; 15:271-86. [DOI: 10.1111/1462-2920.12014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 09/23/2012] [Accepted: 09/27/2012] [Indexed: 11/30/2022]
Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program; Centro Nacional de Biotecnología CSIC; Cantoblanco-Madrid; 28049; Spain
| | - Víctor de Lorenzo
- Systems Biology Program; Centro Nacional de Biotecnología CSIC; Cantoblanco-Madrid; 28049; Spain
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de las Heras A, Fraile S, de Lorenzo V. Increasing signal specificity of the TOL network of Pseudomonas putida mt-2 by rewiring the connectivity of the master regulator XylR. PLoS Genet 2012; 8:e1002963. [PMID: 23071444 PMCID: PMC3469447 DOI: 10.1371/journal.pgen.1002963] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/07/2012] [Indexed: 11/28/2022] Open
Abstract
Prokaryotic transcription factors (TFs) that bind small xenobiotic molecules (e.g., TFs that drive genes that respond to environmental pollutants) often display a promiscuous effector profile for analogs of the bona fide chemical signals. XylR, the master TF for expression of the m-xylene biodegradation operons encoded in the TOL plasmid pWW0 of Pseudomonas putida, responds not only to the aromatic compound but also, albeit to a lesser extent, to many other aromatic compounds, such as 3-methylbenzylalcohol (3MBA). We have examined whether such a relaxed regulatory scenario can be reshaped into a high-capacity/high-specificity regime by changing the connectivity of this effector-sensing TF within the rest of the circuit rather than modifying XylR structure itself. To this end, the natural negative feedback loop that operates on xylR transcription was modified with a translational attenuator that brings down the response to 3MBA while maintaining the transcriptional output induced by m-xylene (as measured with a luxCDABE reporter system). XylR expression was then subject to a positive feedback loop in which the TF was transcribed from its own target promoters, each known to hold different input/output transfer functions. In the first case (xylR under the strong promoter of the upper TOL operon, Pu), the reporter system displayed an increased transcriptional capacity in the resulting network for both the optimal and the suboptimal XylR effectors. In contrast, when xylR was expressed under the weaker Ps promoter, the resulting circuit unmistakably discriminated m-xylene from 3MBA. The non-natural connectivity engineered in the network resulted both in a higher promoter activity and also in a much-increased signal-to-background ratio. These results indicate that the working regimes of given genetic circuits can be dramatically altered through simple changes in the way upstream transcription factors are self-regulated by positive or negative feedback loops. It is generally taken for granted that promoters regulated by transcriptional factors (TFs) that respond to small molecules control their specificity to given effectors by tightening or relaxing the intrinsic dual interaction between the TF and the particular inducer. One such promoter is Pu, which drives expression of an operon for the biodegradation of m-xylene by the soil bacterium P. putida mt-2. While XylR, the chief TF of this system, binds this substrate and activates Pu, the same regulator responds, to a lesser extent, to 3-methylbenzylalcohol and thus also activates the promoter. This work provides evidence that such natural effector promiscuity of the system can be altogether suppressed by replacing the naturally occurring negative autoregulation loop that governs XylR expression with an equivalent positive feedback loop. Based on this result, we argue that signal specificity of a given regulatory device depends not only on the TF involved but also on TF connectivity to upstream signals and downstream targets.
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Affiliation(s)
| | | | - Victor de Lorenzo
- Systems Biology Program, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
- * E-mail:
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Silva-Rocha R, de Lorenzo V. Stochasticity of TOL plasmid catabolic promoters sets a bimodal expression regime inPseudomonas putidamt-2 exposed tom-xylene. Mol Microbiol 2012; 86:199-211. [DOI: 10.1111/j.1365-2958.2012.08184.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Silva-Rocha R, Pérez-Pantoja D, de Lorenzo V. Decoding the genetic networks of environmental bacteria: regulatory moonlighting of the TOL system of Pseudomonas putida mt-2. ISME JOURNAL 2012; 7:229-32. [PMID: 22895160 DOI: 10.1038/ismej.2012.98] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain
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Jurado P, Fernández LA, de Lorenzo V. Production and characterization of a recombinant single-chain antibody (scFv) for tracing the σ54 factor of Pseudomonas putida. J Biotechnol 2012; 160:33-41. [PMID: 22206981 DOI: 10.1016/j.jbiotec.2011.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 12/08/2011] [Accepted: 12/13/2011] [Indexed: 11/26/2022]
Abstract
The number of alternative sigma factor molecules per bacterial cell determines either stochasticity or evenness of transcription of cognate promoters. An approach for examining the abundance of sigmas in any sample of bacterial origin is explained here which relies on the production of a recombinant highly specific, high-affinity single-chain variable Fv domain (scFv) targeted towards unique protein sites of the factor. Purposely, a super-binder scFv recognizing a distinct epitope of the less abundant sigma σ(54) of Pseudomonas putida (also known as σ(N)) was obtained and its properties examined in detail. To this end, an scFv library was generated from mRNA extracted from lymphocytes of mice immunized with the purified σ(54) protein of this bacterium. The library was displayed on a phage system and subjected to various rounds of panning with purified σ(54) for capturing extreme binders. The resulting high-affinity anti-σ(54) phage antibody (Phab) clone named C2 strongly attached a small region located between positions 172 and 183 of the primary amino acid sequence of σ(54) that overlaps its core RNA polymerase-binding region. The purified scFv-C2 detected minute amounts of σ(54) in whole cell protein extracts not only of P. putida but also Escherichia coli cells and putatively in other bacteria as well. The affinity constant of the purified antibody was measured by surface plasmon resonance (SPR) and found to have a K(D) (k(off)/k(on)) in the range of 2×10(-9)M. The considerable affinity and specificity of this recombinant antibody makes it a tool of choice for quantitative studies on gene expression of σ(54)-dependent promoters in P. putida and other Gram-negative bacteria.
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Affiliation(s)
- Paola Jurado
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Darwin 3, Madrid, Spain
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Silva-Rocha R, de Jong H, Tamames J, de Lorenzo V. The logic layout of the TOL network of Pseudomonas putida pWW0 plasmid stems from a metabolic amplifier motif (MAM) that optimizes biodegradation of m-xylene. BMC SYSTEMS BIOLOGY 2011; 5:191. [PMID: 22078029 PMCID: PMC3253710 DOI: 10.1186/1752-0509-5-191] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2011] [Accepted: 11/11/2011] [Indexed: 12/13/2022]
Abstract
Background The genetic network of the TOL plasmid pWW0 of the soil bacterium Pseudomonas putida mt-2 for catabolism of m-xylene is an archetypal model for environmental biodegradation of aromatic pollutants. Although nearly every metabolic and transcriptional component of this regulatory system is known to an extraordinary molecular detail, the complexity of its architecture is still perplexing. To gain an insight into the inner layout of this network a logic model of the TOL system was implemented, simulated and experimentally validated. This analysis made sense of the specific regulatory topology out on the basis of an unprecedented network motif around which the entire genetic circuit for m-xylene catabolism gravitates. Results The most salient feature of the whole TOL regulatory network is the control exerted by two distinct but still intertwined regulators (XylR and XylS) on expression of two separated catabolic operons (upper and lower) for catabolism of m-xylene. Following model reduction, a minimal modular circuit composed by five basic variables appeared to suffice for fully describing the operation of the entire system. In silico simulation of the effect of various perturbations were compared with experimental data in which specific portions of the network were activated with selected inducers: m-xylene, o-xylene, 3-methylbenzylalcohol and 3-methylbenzoate. The results accredited the ability of the model to faithfully describe network dynamics. This analysis revealed that the entire regulatory structure of the TOL system enables the action an unprecedented metabolic amplifier motif (MAM). This motif synchronizes expression of the upper and lower portions of a very long metabolic system when cells face the head pathway substrate, m-xylene. Conclusion Logic modeling of the TOL circuit accounted for the intricate regulatory topology of this otherwise simple metabolic device. The found MAM appears to ensure a simultaneous expression of the upper and lower segments of the m-xylene catabolic route that would be difficult to bring about with a standard substrate-responsive single promoter. Furthermore, it is plausible that the MAM helps to avoid biochemical conflicts between competing plasmid-encoded and chromosomally-encoded pathways in this bacterium.
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Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program, Centro Nacional de Biotecnología CSIC Cantoblanco-Madrid, 28049, Spain
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Silva-Rocha R, de Lorenzo V. A composite feed-forward loop I4-FFL involving IHF and Crc stabilizes expression of the XylR regulator of Pseudomonas putida mt-2 from growth phase perturbations. MOLECULAR BIOSYSTEMS 2011; 7:2982-90. [PMID: 21853168 DOI: 10.1039/c1mb05264k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Genetic networks are typically composed of a series of connected motifs that confer specific logic and dynamic properties to the resulting circuits. While some feed forward loop (FFL) variants abound in such networks, others (e.g. the type-4 incoherent FFL or I4-FFL) are virtually absent from the known regulatory devices. We report here that the key node that rules the expression of the m-xylene biodegradation pathway of the soil bacterium Pseudomonas putida mt-2 merges opposite physiological effects of the growth phase by means of a regulatory device based on the rarely found I4-FFL motif. Specifically, the FFL includes the integration host factor (IHF), which both co-activates the master P(u) promoter and represses transcription of its cognate regulatory gene xylR at the onset of the stationary phase. On the other hand, the catabolite repression control (Crc) protein inhibits translation of XylR during exponential growth. By computing these two conflicting regulatory actions within a composite I4-FFL gate, cells shield the expression of XylR from perturbations caused by the growth phase, thereby ensuring a steady supply of the regulator regardless of physiological conditions. This device thus endows xylR expression with a degree of robustness in respect to the growth phase that could hardly be achieved with e.g. a simple constitutive promoter.
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Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program, Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049, Spain
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Vogne C, Bisht H, Arias S, Fraile S, Lal R, van der Meer JR. Characterisation of the putative effector interaction site of the regulatory HbpR protein from Pseudomonas azelaica by site-directed mutagenesis. PLoS One 2011; 6:e16539. [PMID: 21379585 PMCID: PMC3040749 DOI: 10.1371/journal.pone.0016539] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 12/29/2010] [Indexed: 11/18/2022] Open
Abstract
Bacterial transcription activators of the XylR/DmpR subfamily exert their expression control via σ(54)-dependent RNA polymerase upon stimulation by a chemical effector, typically an aromatic compound. Where the chemical effector interacts with the transcription regulator protein to achieve activation is still largely unknown. Here we focus on the HbpR protein from Pseudomonas azelaica, which is a member of the XylR/DmpR subfamily and responds to biaromatic effectors such as 2-hydroxybiphenyl. We use protein structure modeling to predict folding of the effector recognition domain of HbpR and molecular docking to identify the region where 2-hydroxybiphenyl may interact with HbpR. A large number of site-directed HbpR mutants of residues in- and outside the predicted interaction area was created and their potential to induce reporter gene expression in Escherichia coli from the cognate P(C) promoter upon activation with 2-hydroxybiphenyl was studied. Mutant proteins were purified to study their conformation. Critical residues for effector stimulation indeed grouped near the predicted area, some of which are conserved among XylR/DmpR subfamily members in spite of displaying different effector specificities. This suggests that they are important for the process of effector activation, but not necessarily for effector specificity recognition.
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Affiliation(s)
- Christelle Vogne
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Hansi Bisht
- Department of Zoology, University of Delhi, Delhi, India
| | - Sagrario Arias
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Sofia Fraile
- National Centre for Biotechnology, CSIC, Madrid, Spain
| | - Rup Lal
- Department of Zoology, University of Delhi, Delhi, India
| | - Jan Roelof van der Meer
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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Zafra O, Fraile S, Gutiérrez C, Haro A, Páez-Espino AD, Jiménez JI, de Lorenzo V. Monitoring biodegradative enzymes with nanobodies raised in Camelus dromedarius with mixtures of catabolic proteins. Environ Microbiol 2011; 13:960-74. [DOI: 10.1111/j.1462-2920.2010.02401.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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de las Heras A, de Lorenzo V. Cooperative amino acid changes shift the response of the σ54-dependent regulator XylR from natural m-xylene towards xenobiotic 2,4-dinitrotoluene. Mol Microbiol 2011; 79:1248-59. [DOI: 10.1111/j.1365-2958.2010.07518.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Moreno R, Fonseca P, Rojo F. The Crc global regulator inhibits the Pseudomonas putida pWW0 toluene/xylene assimilation pathway by repressing the translation of regulatory and structural genes. J Biol Chem 2010; 285:24412-9. [PMID: 20529863 PMCID: PMC2915677 DOI: 10.1074/jbc.m110.126615] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 05/13/2010] [Indexed: 11/06/2022] Open
Abstract
In Pseudomonas putida, the expression of the pWW0 plasmid genes for the toluene/xylene assimilation pathway (the TOL pathway) is subject to complex regulation in response to environmental and physiological signals. This includes strong inhibition via catabolite repression, elicited by the carbon sources that the cells prefer to hydrocarbons. The Crc protein, a global regulator that controls carbon flow in pseudomonads, has an important role in this inhibition. Crc is a translational repressor that regulates the TOL genes, but how it does this has remained unknown. This study reports that Crc binds to sites located at the translation initiation regions of the mRNAs coding for XylR and XylS, two specific transcription activators of the TOL genes. Unexpectedly, eight additional Crc binding sites were found overlapping the translation initiation sites of genes coding for several enzymes of the pathway, all encoded within two polycistronic mRNAs. Evidence is provided supporting the idea that these sites are functional. This implies that Crc can differentially modulate the expression of particular genes within polycistronic mRNAs. It is proposed that Crc controls TOL genes in two ways. First, Crc inhibits the translation of the XylR and XylS regulators, thereby reducing the transcription of all TOL pathway genes. Second, Crc inhibits the translation of specific structural genes of the pathway, acting mainly on proteins involved in the first steps of toluene assimilation. This ensures a rapid inhibitory response that reduces the expression of the toluene/xylene degradation proteins when preferred carbon sources become available.
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Affiliation(s)
- Renata Moreno
- From the Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas (CSIC), Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Pilar Fonseca
- From the Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas (CSIC), Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Fernando Rojo
- From the Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas (CSIC), Campus Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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Bernardo LMD, Johansson LUM, Skärfstad E, Shingler V. sigma54-promoter discrimination and regulation by ppGpp and DksA. J Biol Chem 2008; 284:828-38. [PMID: 19008221 DOI: 10.1074/jbc.m807707200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sigma(54)-factor controls expression of a variety of genes in response to environmental cues. Much previous work has implicated the nucleotide alarmone ppGpp and its co-factor DksA in control of sigma(54)-dependent transcription in the gut commensal Escherichia coli, which has evolved to live under very different environmental conditions than Pseudomonas putida. Here we compared ppGpp/DksA mediated control of sigma(54)-dependent transcription in these two organisms. Our in vivo experiments employed P. putida mutants and manipulations of factors implicated in ppGpp/DksA mediated control of sigma(54)-dependent transcription in combination with a series of sigma(54)-promoters with graded affinities for sigma(54)-RNA polymerase. For in vitro analysis we used a P. putida-based reconstituted sigma(54)-transcription assay system in conjunction with DNA-binding plasmon resonance analysis of native and heterologous sigma(54)-RNA polymerase holoenzymes. In comparison with E. coli, ppGpp/DksA responsive sigma(54)-transcription in the environmentally adaptable P. putida was found to be more robust under low energy conditions that occur upon nutrient depletion. The mechanism behind this difference can be traced to reduced promoter discrimination of low affinity sigma(54)-promoters that is conferred by the strong DNA binding properties of the P. putida sigma(54)-RNA polymerase holoenzyme.
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Jones J, Studholme DJ, Knight CG, Preston GM. Integrated bioinformatic and phenotypic analysis of RpoN-dependent traits in the plant growth-promoting bacterium Pseudomonas fluorescens SBW25. Environ Microbiol 2007; 9:3046-64. [DOI: 10.1111/j.1462-2920.2007.01416.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Garcillán-Barcia MP, Jurado P, González-Pérez B, Moncalián G, Fernández LA, de la Cruz F. Conjugative transfer can be inhibited by blocking relaxase activity within recipient cells with intrabodies. Mol Microbiol 2006; 63:404-16. [PMID: 17163977 DOI: 10.1111/j.1365-2958.2006.05523.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Horizontal transfer of antibiotic resistance genes carried by conjugative plasmids poses a serious health problem. As conjugative relaxases are transported to recipient cells during bacterial conjugation, we investigated whether blocking relaxase activity in the recipient cell might inhibit conjugation. For that purpose, we used an intrabody approach generating a single-chain Fv antibody library against the relaxase TrwC of conjugative plasmid R388. Recombinant single-chain Fv antibodies were engineered for cytoplasmic expression in Escherichia coli cells and either selected in vitro for their specific binding to TrwC, or in vivo by their ability to interfere with conjugation using a high-throughput mating assay. Several intrabody clones were identified showing specific inhibition against R388 conjugation upon cytoplasmic expression in the recipient cell. The epitope recognized by one of these intrabodies was mapped to a region of TrwC containing Tyr-26 and involved in the conjugative DNA-processing termination reaction. These findings demonstrate that the transferred relaxase plays an important role in the recipient cell and open a new approach to identify specific inhibitors of bacterial conjugation.
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Affiliation(s)
- M Pilar Garcillán-Barcia
- Departamento de Biología Molecular (Laboratorio asociado al Centro de Investigaciones Biológicas, C.S.I.C.), Universidad de Cantabria, C/Cardenal Herrera Oria s/n, 39011 Santander, Spain
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20
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Imai S, Mukai Y, Nagano K, Shibata H, Sugita T, Abe Y, Nomura T, Tsutsumi Y, Kamada H, Nakagawa S, Tsunoda SI. Quality enhancement of the non-immune phage scFv library to isolate effective antibodies. Biol Pharm Bull 2006; 29:1325-30. [PMID: 16819162 DOI: 10.1248/bpb.29.1325] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The non-immune phage antibody library system is one of the most attractive technologies available to current therapeutic, diagnostic and basic scientific research. This system allows the rapid isolation of antibodies of interest that could subsequently be applied directly to drug delivery systems and antibody therapy. Previously, we reported the primer sets to encompass the antibody repertoire and thus improve library quality. However, a wide number of varying primer sets cause to decrease the amplification efficiency of antibody genes. In the present study, we re-generated the library primer sets newly and constructed an improved library from non-immune mice that was far superior in terms of variety and quality. This new library contained 2.4 billion independent clones. In addition, we optimized the selection step from this library to isolate high-affinity antibodies. The optimization of an affinity panning protocol by the incorporation of an automated Microfluidics instrument led to the successful isolation of three different monoclonal antibodies for human vascular endothelial growth factor receptor 2 (KDR). These antibodies were demonstrated to exhibit high specificity and were able to detect a mere 0.6 fmol of KDR by dot blot analysis. Previously reported antibodies for luciferase were also isolated successfully from this library. Our results clearly demonstrate the importance of the improved protocol for the library preparation of antibodies and the resulting isolation of antibodies for clinical and research applications.
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Affiliation(s)
- Sunao Imai
- Laboratory of Pharmaceutical Proteomics, National Institute of Biomedical Innovation, Osaka, Japan
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21
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Jurado P, Fernández LA, de Lorenzo V. In vivo drafting of single-chain antibodies for regulatory duty on the sigma54-promoter Pu of the TOL plasmid. Mol Microbiol 2006; 60:1218-27. [PMID: 16689797 DOI: 10.1111/j.1365-2958.2006.05183.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The identification of single-chain antibodies (scFvs) that interfere in vivo with the building of the complex that activate the prokaryotic, sigma54-dependent promoter Pu of the catabolic TOL plasmid pWW0 is reported. To this end, a phage M13 library of scFvs was raised against the cognate prokaryotic enhancer-binding activator, XylR. The scFv pool was then expressed intracellularly in a reporter Pu-lacZ strain of Escherichia coli designed to permit formation of intramolecular disulphide bonds in cytoplasmic proteins. This strain allowed the assembly of functional scFvs and the direct testing of their activity on the Pu promoter in vivo. Specifically, genetic screening for lacZ-minus colonies yielded a number of scFvs able to downregulate transcriptional output in live cells. Two antibody clones were purified and shown to inhibit the activity of the same promoter in vitro as well. These scFvs targeted the DNA-binding domain of XylR and its ATP binding site respectively. This work provides a proof of principle that mimetic regulatory factors can be derived from an antibody repertoire that specifically interact with given transcriptional activators. As assembly of initiation complexes is stimulated or inhibited by regulatory proteins we argue that anti-XylR scFvs operate as bona fide transcriptional inhibitors of the Pu promoter.
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Affiliation(s)
- Paola Jurado
- Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049, Spain
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22
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Velázquez F, Fernández S, de Lorenzo V. The upstream-activating sequences of the sigma54 promoter Pu of Pseudomonas putida filter transcription readthrough from upstream genes. J Biol Chem 2006; 281:11940-8. [PMID: 16510445 DOI: 10.1074/jbc.m511782200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Although the m-xylene-responsive sigma54 promoter Pu of Pseudomonas putida mt-2, borne by the TOL plasmid pWWO, is one of the strongest known promoters in vivo, its base-line level in the absence of its aromatic inducer is below the limit of any detection procedure. This is unusual because regulatory networks (such as the one to which Pu belongs) can hardly escape the noise caused by intrinsic fluctuations in background transcription, including that transmitted from upstream promoters. This study provides genetic evidence that the upstream-activating sequences (UAS), which serve as the binding sites for the pWW0-encoded XylR protein (the m-xylene-responsive sigma54-dependent activator of Pu), isolate expression of the upper TOL genes from any adventitious transcriptional flow originating further upstream. An in vivo test system was developed in which different segments of the Pu promoter were examined for the inhibition of incoming transcription products from an upstream promoter in P. putida and Escherichia coli. Minimal transcription filter ability was located within a 105-bp fragment encompassing the UAS of Pu. Although S1 nuclease assays showed that the UAS prevented the buildup of downstream transcripts, the mechanism seems to diverge from a typical termination system. This was shown by the fact that the UAS did not halt transcription in vitro and that the filter effect could not be relieved by the anti-termination system of lambda phage. Because the Pu promoter lies adjacent to the edge of a transposon in pWW0, the preset transcriptional filter in the UAS may isolate the upper TOL operon from undue expression after random insertion of the mobile genetic element in a new replicon.
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Affiliation(s)
- Francisco Velázquez
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus UAM-Cantoblanco, 28049 Madrid, Spain
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23
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Jurado P, de Lorenzo V, Fernández LA. Thioredoxin fusions increase folding of single chain Fv antibodies in the cytoplasm of Escherichia coli: evidence that chaperone activity is the prime effect of thioredoxin. J Mol Biol 2006; 357:49-61. [PMID: 16427080 DOI: 10.1016/j.jmb.2005.12.058] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 12/14/2005] [Accepted: 12/16/2005] [Indexed: 11/21/2022]
Abstract
In this study we investigate the effect of thioredoxin (Trx1) protein fusions in the production, oxidation, and folding of single chain Fv (scFv) antibodies in the cytoplasm of Escherichia coli. We analyze the expression levels, solubility, disulfide-bond formation, and antigen-binding properties of Trx1-scFv fusions in E. coli wild-type cells and isogenic strains carrying mutations in the glutathione oxidoreductase (gor) and/or thioredoxin reductase (trxB) genes. We compare the Trx1-scFv fusions with other reported systems for production of scFv in the cytoplasm of E. coli, including protein fusions to the maltose-binding protein. In addition, we analyze the effect of co-expressing a signal-sequence-less derivative of the periplasmic chaperone and disulfide-bond isomerase DsbC (DeltassDsbC), which has been shown to act as a chaperone for scFvs in the cytoplasm. The results reported here demonstrate that Trx1 fusions produce the highest expression level and induce the correct folding of scFvs even in the absence of DeltassDsbC in the cytoplasm of E. coli trxB gor cells. The disulfide bridges of Trx1-scFv fusions were formed correctly in E. coli trxB gor cells, but not in trxB single mutants. Antigen-binding assays showed that Trx1 has only a minor influence in the affinity of the scFv, indicating that Trx1-scFv fusions can be used without removal of the Trx1 moiety. In addition, we proved that a Trx1"AGPA" variant, having its catalytic cysteine residues mutated to alanine, was fully capable of assisting the folding of the fused scFvs. Taken together, our data indicate that the Trx1 moiety acts largely as an intramolecular protein chaperone, not as a disulfide bond catalyst, inducing the correct folding of scFvs in the cytoplasm of E. coli trxB gor cells.
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Affiliation(s)
- Paola Jurado
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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24
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Solera D, Arenghi FLG, Woelk T, Galli E, Barbieri P. TouR-mediated effector-independent growth phase-dependent activation of the sigma54 Ptou promoter of Pseudomonas stutzeri OX1. J Bacteriol 2004; 186:7353-63. [PMID: 15489447 PMCID: PMC523194 DOI: 10.1128/jb.186.21.7353-7363.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of the catabolic touABCDEF operon, encoding the toluene-o-xylene monooxygenase of Pseudomonas stutzeri OX1, is driven by the sigma(54)-dependent Ptou promoter, whose activity is controlled by the phenol-responsive NtrC-like activator TouR. In this paper we describe for the first time a peculiar characteristic of this system, namely, that Ptou transcription is activated in a growth phase-dependent manner in the absence of genuine effectors of the cognate TouR regulator. This phenomenon, which we named gratuitous activation, was observed in the native strain P. stutzeri OX1, as well as in a Pseudomonas putida PaW340 host harboring the reconstructed tou regulatory circuit. Regulator-promoter swapping experiments demonstrated that the presence of TouR is necessary and sufficient for imposing gratuitous activation on the Ptou promoter, as well as on other sigma(54)-dependent catabolic promoters, whereas the highly similar phenol-responsive activator DmpR is unable to activate the Ptou promoter in the absence of effectors. We show that this phenomenon is specifically triggered by carbon source exhaustion but not by nitrogen starvation. An updated model of the tou regulatory circuit is presented.
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Affiliation(s)
- Dafne Solera
- Dipartimento di Biologia Strutturale e Funzionale, Università degli Studi di Milano, Milan, Italy
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25
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Tropel D, van der Meer JR. Bacterial transcriptional regulators for degradation pathways of aromatic compounds. Microbiol Mol Biol Rev 2004; 68:474-500, table of contents. [PMID: 15353566 PMCID: PMC515250 DOI: 10.1128/mmbr.68.3.474-500.2004] [Citation(s) in RCA: 295] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human activities have resulted in the release and introduction into the environment of a plethora of aromatic chemicals. The interest in discovering how bacteria are dealing with hazardous environmental pollutants has driven a large research community and has resulted in important biochemical, genetic, and physiological knowledge about the degradation capacities of microorganisms and their application in bioremediation, green chemistry, or production of pharmacy synthons. In addition, regulation of catabolic pathway expression has attracted the interest of numerous different groups, and several catabolic pathway regulators have been exemplary for understanding transcription control mechanisms. More recently, information about regulatory systems has been used to construct whole-cell living bioreporters that are used to measure the quality of the aqueous, soil, and air environment. The topic of biodegradation is relatively coherent, and this review presents a coherent overview of the regulatory systems involved in the transcriptional control of catabolic pathways. This review summarizes the different regulatory systems involved in biodegradation pathways of aromatic compounds linking them to other known protein families. Specific attention has been paid to describing the genetic organization of the regulatory genes, promoters, and target operon(s) and to discussing present knowledge about signaling molecules, DNA binding properties, and operator characteristics, and evidence from regulatory mutants. For each regulator family, this information is combined with recently obtained protein structural information to arrive at a possible mechanism of transcription activation. This demonstrates the diversity of control mechanisms existing in catabolic pathways.
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Affiliation(s)
- David Tropel
- Swiss Federal Institute for Environmental Science and Technology (EAWAG), Dübendorf, Switzerland
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26
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Fraile S, Muñoz A, de Lorenzo V, Fernández LA. Secretion of proteins with dimerization capacity by the haemolysin type I transport system of Escherichia coli. Mol Microbiol 2004; 53:1109-21. [PMID: 15306015 DOI: 10.1111/j.1365-2958.2004.04205.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The tolerance of the haemolysin transport system (Hly) for exporting dimeric protein substrates to the supernatants of Escherichia coli cultures was examined. A strong dimerization domain (i.e. an amphipathic alpha-helix capable of forming a leucine zipper in the yeast transcription factor GCN4) was inserted into an epitope-tagged version of the 23 kDa C-terminal secretion signal of haemolysin (EHlyA). The zipper-containing polypeptide (ZEHlyA) was effectively secreted by E. coli cells carrying the HlyBD transporter and accumulated in the culture media as a stable dimer as determined by gel filtration chromatography. In vivo protein cross-linking experiments and coexpression with a secretion-deficient derivative of ZEHlyA indicated that leucine zipper-dependent dimerization occurs following secretion. To test whether dimerization allows the correct folding of the secreted polypeptide, immunoglobulin V(HH)-domains obtained from camel antibodies were fused to EHlyA and ZEHlyA. Functional dimerization of the ZEHlyA hybrid was anticipated to increase the apparent binding affinity (i.e. avidity) of the V(HH) moiety, thus becoming an excellent reporter of correct protein folding and dimerization. Both V(HH)-EHlyA and V(HH)-ZEHlyA hybrids were quantitatively secreted and found in the extracellular medium as active monomers and dimers respectively. When compared with their monomeric counterparts, the dimeric V(HH)-ZEHlyA molecules showed superior binding properties to their cognate antigen, with a 10-fold increase in their avidity. These data reveal a non-anticipated permissiveness of the Hly type I transport machinery for the secretion of substrates with dimerization capacity.
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Affiliation(s)
- Sofía Fraile
- Centro Nacional de Biotecnología del Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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27
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Valls M, de Lorenzo V. Transient XylR binding to the UAS of the Pseudomonas putida sigma54 promoter Pu revealed with high intensity UV footprinting in vivo. Nucleic Acids Res 2003; 31:6926-34. [PMID: 14627825 PMCID: PMC290279 DOI: 10.1093/nar/gkg912] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 10/16/2003] [Accepted: 10/16/2003] [Indexed: 11/12/2022] Open
Abstract
The binding of the transcriptional regulator XylR to its cognate upstream activating sequences (UAS) of the sigma54-dependent promoter Pu of Pseudomonas putida has been examined in vivo in single copy gene dose and stoichiometry. To this end, we have employed a novel in vivo genomic footprinting procedure that uses short exposures of bacterial cells to diffuse high intensity UV light that causes formation of TT or TC dimers. In contrast to simpler models for activation of sigma54-dependent promoters, our results clearly indicate that the XylR protein is not permanently bound in vivo to its target sites in Pu. On the contrary, the UAS appear to be mostly unoccupied at all growth stages. This is in contrast to the integration host factor (IHF), which binds Pu strongly in vivo at stationary phase, as also revealed by UV footprinting. Only overexpression of XylR altered the photoreactivity of the corresponding DNA region to report stable binding of the regulator to the UAS. However, the presence of aromatic XylR inducers reversed the forced occupation caused by increased levels of the activator. These results are compatible with the notion that XylR interacts very transiently with the UAS and detaches from the promoter during transcriptional activation of Pu.
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Affiliation(s)
- Marc Valls
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología del Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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28
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Van Dien SJ, de Lorenzo V. Deciphering environmental signal integration in sigma54-dependent promoters with a simple mathematical model. J Theor Biol 2003; 224:437-49. [PMID: 12957116 DOI: 10.1016/s0022-5193(03)00191-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A mathematical model was developed to describe the physiological co-regulation of two Pseudomonas sigma54-dependent promoter/regulator systems, Pu/XylR and Po/DmpR of Pseudomonas strains mt2 and CF600, respectively. Five ordinary differential equations and six algebraic equations were developed to describe the following processes of transcription initiation: binding of the activator protein to the upstream activating sequence, union of the sigma factor with the core polymerase, formation of the open complex, and escape of the transcription machinery from the promoter region. In addition, growth-phase control of the integration host factor (IHF), sigma-70 regulation during stationary phase, and the contribution of (p)ppGpp to both sigma factor selectivity and promoter escape were hypothesized. By including any three of these four effects, the model predicted that expression from both promoters is repressed during exponential growth and sharply increases as the cells enter stationary phase. The difference in behavior of the two systems during overexpression of either sigma54 or (p)ppGpp could be explained by different values of two model parameters. To accurately represent the behavior of both promoters in (p)ppGpp null strains, an additional parameter must be varied. Although numerical data available for this system is scarce, the model has proved useful for helping to interpret the experimental observations and to evaluate four hypotheses that have been proposed to explain the phenomenon of exponential silencing.
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Affiliation(s)
- Stephen J Van Dien
- Centro Nacional de Biotecnología, Campus Universidad Autónoma, 28049 Madrid, Spain.
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29
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Jurado P, Ritz D, Beckwith J, de Lorenzo V, Fernández LA. Production of functional single-chain Fv antibodies in the cytoplasm of Escherichia coli. J Mol Biol 2002; 320:1-10. [PMID: 12079330 DOI: 10.1016/s0022-2836(02)00405-9] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Production of intracellular antibodies in Escherichia coli has been thought unlikely owing to an inability to form stable disulfide bonds in the cytoplasm, a necessary step in the folding of most immunoglobulin (Ig) domains. This work investigates whether E. coli strains carrying mutations in the major intracellular disulfide bond-reduction systems (i.e. the thioredoxin and the glutathione/glutaredoxin pathways) allow the oxidation and folding of single chain variable fragment (scFv) antibodies in the cytoplasm. The effect of the co-expression of disulfide bond chaperones in these cells was also examined. An scFv that recognizes the alternative sigma factor sigma(54) was used as a model to investigate disulfide bond formation and the folding of Ig domains in E. coli. The results demonstrate that functional intrabodies, with oxidized disulfide bonds in their Ig domains, are produced efficiently in E. coli cells carrying mutations in the glutathione oxidoreductase (gor) and the thioredoxin reductase (trxB) genes and co-expressing a signal-sequence-less derivative of the disulfide-bond isomerase DsbC ((Delta)ssDsbC). We obtained evidence indicating that (Delta)ssDsbC acts as a chaperone promoting the correct folding and oxidation of scFvs.
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Affiliation(s)
- Paola Jurado
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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30
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Garmendia J, Devos D, Valencia A, de Lorenzo V. A la carte transcriptional regulators: unlocking responses of the prokaryotic enhancer-binding protein XylR to non-natural effectors. Mol Microbiol 2001; 42:47-59. [PMID: 11679066 DOI: 10.1046/j.1365-2958.2001.02633.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To investigate the activation mechanism of the enhancer-binding protein XylR encoded by the TOL plasmid of Pseudomonas putida mt-2, a combinatorial library was generated composed of shuffled N-terminal A domains of the homologous regulators DmpR, XylR and TbuT, reassembled within the XylR structure. When the library was screened in vivo for responsiveness to non-effectors bulkier than one aromatic ring (such as biphenyl) or bearing an entirely different distribution of electronegative groups (e.g. nitrotoluenes), protein variants were found that displayed an expanded inducer range including the new effectors. Although the phenotypes endowed with the corresponding changes were largely similar, the modifications involved different sites within the A domain. The positions of the mutations within a structural model of the A domain suggest that expansion of the inducer profile can be brought about not only by changes in the effector pocket of the protein but also by unlocking steps of the signal transmission mechanism that follows effector binding. These results provide a rationale for evolving in vitro regulators à la carte that are responsive to predetermined, natural or xenobiotic chemical species.
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Affiliation(s)
- J Garmendia
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
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