Part:BBa_K1513002
Hg(II) sensor
Our part is based on the mechanism of merOP regulator, which is as following. The current model for MerR activation of transcription proposes that expression of MerR (in the absence of MerR and Hg (II) in the cell) proceeds from the PmerR promoter. In the absence of Hg(II), the MerR homodimer binds to the operator region within the divergent promoter with binding centered on the dyad symmetrical DNA sequence between the -35 and -10 sequences of PmerT, slightly repressing transcription of the structural gene promoter, and repressing transcription of merR from the PmerR promoter. In the absence of Hg(II), the tight binding of the apo-MerR homodimer to PmerT causes a further bending of the promoter DNA to itself, making it even less ideal for RNAP binding. Once the MerR homodimer has bound to merOP, recruitment of RNAP to the mer promoter occurs, and MerR has been shown to cross-link to several subunits of RNAP. In the absence of Hg(II) the ternary complex of MerR, RNAP, and merOP represses transcription of the mer structural genes. In the presence of mercuric ions, one Hg(II) per MerR homodimer coordinates in a trigonal manner to three essential cysteine residues of the MerR homodimer, two cysteines from one monomer, and one from the other. Hg(II) binding to the MerR homodimer results in both a relaxation of the DNA bends induced by apo-MerR, and both DNA distortion and an allosteric underwinding of the promoter sequence by approximately 33. The underwinding of the promoter DNA aligns the -10 and -35 sequences, such that RNA polymerase can recognize and bind to these sites, initiating transcription from PmerT .
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI.rc site found at 1184
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