The Molecular Switch of Telomere Phages: High Binding Specificity of the PY54 Cro Lytic Repressor to a Single Operator Site

ABSTRACT The torECAD operon encoding the trimethylamine oxide (TMAO) respiratory system of Shewanella oneidensis is positively controlled by the TorS/TorR two-component system when TMAO is available. Activation of the tor operon occurs upon binding of the phosphorylated response regulator TorR to a single operator site containing the direct repeat nucleotide sequence TTCATAN4TTCATA. Here we show that the replacement of any nucleotide of one TTCATA hexamer prevented TorR binding in vitro, meaning that TorR specifically interacts with this DNA target. Identical direct repeat sequences were found in the promoter regions of torR and of the new gene torF (SO4694), and they allowed TorR binding to both promoters. Real-time PCR experiments revealed that torR is negatively autoregulated, whereas torF is strongly induced by TorR in response to TMAO. Transcription start site location and footprinting analysis indicate that the operator site at torR overlaps the promoter −10 box, whereas the operator site at torF is centered at −74 bp from the start site, in agreement with the opposite role of TorR in the regulation of the two genes. Since torF and torECAD are positively coregulated by TorR, we propose that the TorF protein plays a role related to TMAO respiration.

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REGULATION OF THE put OPERON IN SALMONELLA TYPHIMURIUM: CHARACTERIZATION OF PROMOTER AND OPERATOR MUTATIONS

Genetics ◽

10.1093/genetics/114.3.687 ◽

1986 ◽

Vol 114 (3) ◽

pp. 687-703

Author(s):

Donald R Hahn ◽

Stanley R Maloy

Keyword(s):

Regulatory Region ◽

Lacz Expression ◽

Proline Utilization ◽

Single Operator ◽

Regulatory Mutations ◽

Operon Regulation ◽

In Trans ◽

Operon Expression ◽

Operator Site

ABSTRACT The two genes required for proline utilization by S. typhimurium form a divergent operon. Expression of the put operon is induced by proline and subject to catabolite repression. Genetic evidence suggests that putA protein autogenously represses transcription of the putA and putP genes. In order to establish the molecular mechanism of put operon regulation we isolated regulatory mutations in the put control region. These mutants were selected using two phenotypes: (1) the ability to degrade a toxic proline analogue, dehydroproline, due to overexpression of putA enzyme activity, or (2) overexpression of lacZ from put::Mud operon fusions. The effect of each mutation on transcription in both directions was determined by measuring lacZ expression from putA and putP operon fusions. These regulatory mutations were cis-dominant when the putA protein was provided in trans, and they map in a region between the two genes. The phenotypes of the mutants suggest that (1) the put regulatory region has a single operator site where the putA protein binds to repress transcription in both directions, and (2) the putA and putP promoters overlap.

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Quantification of silk protein using phage nanofibers with high binding specificity

Journal of Materials Chemistry B ◽

10.1039/c9tb01783f ◽

2020 ◽

Vol 8 (24) ◽

pp. 5189-5194 ◽

Cited By ~ 1

Author(s):

Lu Ma ◽

Tao Yang ◽

Mengmeng Zhai ◽

Mingying Yang ◽

Chuanbin Mao

Keyword(s):

Binding Specificity ◽

Silk Protein ◽

Ultrasensitive Detection ◽

Silk Sericin ◽

High Binding ◽

Detection Strategy ◽

Binding Peptides

An ultrasensitive detection strategy for silk sericin (SS) is established by using phage nanofibers displaying SS-binding peptides derived from biopanning. SS concentration is determined by counting the plaques developed from the SS-binding phages.

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