Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/28191
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Type: Journal article
Title: The helix-turn-helix motif of the coliphage 186 immunity repressor binds to two distinct recognition sequences
Author: Shearwin, K.E.
Dodd, I.B.
Egan, J.B.
Citation: Journal of Biological Chemistry, 2002; 277(5):3186-3194
Publisher: American Society for Biochemistry and Molecular Biology
Issue Date: 2002
ISSN: 1083-351X
0021-9258
Statement of
Responsibility: 
Keith E. Shearwin, Ian B. Dodd, and J. Barry Egan
Abstract: The CI protein of coliphage 186 is responsible for maintaining the stable lysogenic state. To do this CI must recognize two distinct DNA sequences, termed A type sites and B type sites. Here we investigate whether CI contains two separate DNA binding motifs or whether CI has one motif that recognizes two different operator sequences. Sequence alignment with 186-like repressors predicts an N-terminal helix-turn-helix (HTH) motif, albeit with poor homology to a large master set of such motifs. The domain structure of CI was investigated by linker insertion mutagenesis and limited proteolysis. CI consists of an N-terminal domain, which weakly dimerizes and binds both A and B type sequences, and a C-terminal domain, which associates to octamers but is unable to bind DNA. A fusion protein consisting of the 186 N-terminal domain and the phage {lambda} oligomerization domain binds A and B type sequences more efficiently than the isolated 186 CI N-terminal domain, hence the 186 C-terminal domain likely mediates oligomerization and cooperativity. Site-directed mutation of the putative 186 HTH motif eliminates binding to both A and B type sites, supporting the idea that binding to the two distinct DNA sequences is mediated by a variant HTH motif.
Keywords: Escherichia coli; Coliphages; DNA-Binding Proteins; Recombinant Proteins; Viral Proteins; DNA Primers; Chromosome Mapping; Mutagenesis, Insertional; Sequence Alignment; Binding Sites; Amino Acid Sequence; Base Sequence; Helix-Turn-Helix Motifs; Zinc Fingers; Sequence Homology, Amino Acid; Kinetics; Molecular Sequence Data; Promoter Regions, Genetic
Rights: © 2002 Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology
RMID: 0020020924
DOI: 10.1074/jbc.M107740200
Appears in Collections:Molecular and Biomedical Science publications

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