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Journal of Bacteriology, September 2008, p. 5890-5897, Vol. 190, No. 17
0021-9193/08/$08.00+0 doi:10.1128/JB.00459-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Department of Frontier Bioscience, Hosei University, Koganei, Tokyo 184-8584, Japan
Received 3 April 2008/ Accepted 13 June 2008
N-Ethylmaleimide (NEM) has been used as a specific reagent of Cys modification in proteins and thus is toxic for cell growth. On the Escherichia coli genome, the nemA gene coding for NEM reductase is located downstream of the gene encoding an as-yet-uncharacterized transcription factor, YdhM. Disruption of the ydhM gene results in reduction of nemA expression even in the induced state, indicating that the two genes form a single operon. After in vitro genomic SELEX screening, one of the target recognition sequences for YdhM was identified within the promoter region for this ydhM-nemA operon. Both YdhM binding in vitro to the ydhM promoter region and transcription repression in vivo of the ydhM-nemA operon by YdhM were markedly reduced by the addition of NEM. Taken together, we propose that YdhM is the repressor for the nemA gene, thus hereafter designated NemR. The repressor function of NemR was inactivated by the addition of not only NEM but also other Cys modification reagents, implying that Cys modification of NemR renders it inactive. This is an addition to the mode of controlling activity of transcription factors by alkylation with chemical agents.
Published ahead of print on 20 June 2008.
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