Control of Vibrio fischeri bioluminescence : genetic analysis of the LuxR protein and the mechanism of transcriptional autoregulation of the LuxR gene /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Expression of bioluminescence in Vibrio fischeri is primarily controlled through two transcriptional autoregulatory circuits, one positive and one negative, which together comprise a cell-density-dependent expression mechanism called autoinduction. Both of these circuits are mediated by the regulatory protein LuxR and a co-activator molecule called autoinducer. The lux regulon consists of two divergently transcribed operons, designated operon[R] (rightward) and operon[L] (leftward), separated by a common regulatory region. The LuxR protein is encoded by the single known gene in operon[L], luxR. Operon[R] consists of seven genes (luxICDABEG) which encode the enzymes required for light production (luxCDABE) and autoinducer synthesis (luxl). In the presence of autoinducer, LuxR binds the lux operator and activates transcription of operon[R]. Since luxl is in operon[R], autoinducer stimulates an increase in its own synthesis and initiates a positive feedback circuit. Transcription of operon[L] (luxR) is negatively regulated by LuxR and autoinducer and activated by the cAMP-CAP global regulatory system. The results presented in this thesis provide a more detailed description of the regulatory components and interactions involved in autoinduction. A genetic selection, based on regulated cell lysis, was designed which allowed the isolation of lux regulatory mutants. Using this selection, mutations in luxR were recovered which allowed an autoinducer-binding region of the LuxR protein to be defined. By DNase I footprinting in vitro, the CAP-binding site was located in the lux control region and the LexA protein was shown to bind the lux operator. Transcription of operonL was found to be inhibited at high levels of LuxR and autoinducer and stimulated at low levels of LuxR and autoinducer. Therefore, luxR exhibits both positive and negative autoregulation. Positive autoregulation required the lux operator and occurred by a CAP-independent mechanism. Negative autoregulation required the lux operator and a lux operator-like sequence located >2 kb upstream of the control region in the luxD gene. A revised model describing lux regulation is proposed to incorporate these new regulatory features. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Biochemistry." |
| Physical Description: | xiv, 173 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |