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dc.contributor.authorGuazzaroni, María Eugenia-
dc.contributor.authorKrell, Tino-
dc.contributor.authorFelipe, Antonia-
dc.contributor.authorRuiz, Raquel-
dc.contributor.authorMeng, Cuixiang-
dc.contributor.authorZhang, Xiaodong-
dc.contributor.authorGallegos, María Trinidad-
dc.contributor.authorRamos, Juan L.-
dc.identifier.citationJournal of Biological Chemistry 280(21): 20887-20893 (2005)en_US
dc.description7 pages, 4 figures, 4 tables.-- Printed version published May 27, 2005.-- Full-text paper available Open Access at the journal site.en_US
dc.description.abstractTtgV modulates the expression of the ttgGHI operon, which encodes an efflux pump that extrudes a wide variety of chemicals including mono- and binuclear aromatic hydrocarbons, aliphatic alcohols, and antibiotics of dissimilar chemical structure. Using a 'lacZ fusion to the ttgG promoter, we show that the most efficient in vivo inducers were 1-naphthol, 2,3-dihydroxynaphthalene, 4-nitrotoluene, benzonitrile, and indole. The thermodynamic parameters for the binding of different effector molecules to purified TtgV were determined by isothermal titration calorimetry. For the majority of effectors, the interaction was enthalpy-driven and counterbalance by unfavorable entropy changes. The TtgV-effector dissociation constants were found to vary between 2 and 890 µM. There was a relationship between TtgV affinity for the different effectors and their potential to induce gene expression in vivo, indicating that the effector binding constant is a major determinant for efficient efflux pump gene expression. Equilibrium dialysis and isothermal titration calorimetry studies indicated that a TtgV dimer binds one effector molecule. No evidence for the simultaneous binding of multiple effectors to TtgV was obtained. The binding of TtgV to a 63-bp DNA fragment containing its cognate operator was tight and entropy-driven (KD = 2.4 ± 0.35 nM, ΔH = 5.5 ± 0.04 kcal/mol). The TtgV-DNA complex was shown to bind 1-napthol with an affinity comparable with the free soluble TtgV protein, KD = 4.8 ± 0.19 and 3.0 ± 0.15 µM, respectively. The biological relevance of this finding is discussed.en_US
dc.description.sponsorshipThis work was supported by EC Project QLK3-CT-2001-0435 (to J. L. R.) and Grant RGY0021/2002 from the Human Frontier Science Program (to M. T. G. and X. Z.).en_US
dc.format.extent328628 bytes-
dc.publisherAmerican Society for Biochemistry and Molecular Biologyen_US
dc.titleThe multidrug efflux regulator TtgV recognizes a wide range of structurally different effectors in solution and complexed with target DNA: evidence from isothermal titration calorimetryen_US
dc.description.peerreviewedPeer revieweden_US
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