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The Escherichia coli regulatory protein OxyR discriminates between methylated and unmethylated states of the phage Mu mom promoter.
Author(s) -
Bölker M.,
Kahmann R.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb08370.x
Subject(s) - biology , escherichia coli , escherichia coli proteins , bacteriophage , microbiology and biotechnology , operon , bacterial protein , dna binding protein , genetics , gene , transcription factor
Expression of the phage Mu mom gene is transcriptionally regulated by DNA methylation. Three GATC sites upstream of the mom promoter have to be methylated by the Escherichia coli deoxyadenosine methylase (Dam) to allow initiation of transcription. An E. coli dam strain was mutagenized with Tn5 in an attempt to isolate mutants which allow mom gene expression. Three independent Tn5 mutants were isolated, each mapped to a gene at 89.6 min which we designate momR. The wildtype gene was cloned and sequenced, it encodes a protein of 305 amino acids. The protein belongs to a group of related bacterial activators recently identified as the LysR family (Henikoff et al., 1988). MomR protein was overproduced and purified. Expression of momR is autoregulated; MomR binds to a 43 bp region upstream of its coding sequence. In the mom promoter MomR protects a 43 bp region containing the three GATC sites. Specific binding to these sequences was observed only with unmethylated DNA. Fortuitously, we learned that MomR is identical to OxyR, a regulatory protein responding to oxidative stress. We discuss the implications of this control for Mu development.