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Functional Studies on Escherichia coli Protein NsrR, a Novel Nitric Oxide Sensitive Transcriptional Repressor
Author(s) -
Bitoun Jacob Philip,
Duan Xeuwu,
Ding Huangen
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.lb201
Subject(s) - chemistry , escherichia coli , repressor , cysteine , nitric oxide , biochemistry , gene , gene expression , enzyme , organic chemistry
NsrR, a novel transcriptional repressor from Escherichia coli , coordinates a solvent exposed [2Fe‐2S] cluster through three highly conserved cysteine residues. In the presence of nitric oxide (NO), the iron‐sulfur cluster in NsrR is modified to form a dinitroysl iron complex, and transcriptional repression of NsrR is relieved, promoting the expression of NO detoxifying and defense genes. Here it is shown that NO modification of purified recombinant NsrR occurs at a higher rate than other iron‐sulfur proteins. This result suggests that the NsrR[2Fe‐2S] cluster could be a primary target of NO cytotoxicity. The redox midpoint potential of the NsrR [2Fe‐2S] cluster was determined to be ‐346 ± 7 mV under anaerobic conditions, indicating that in vivo the [2Fe‐2S] in NsrR could be in its reduced state. The mobility shift analysis indicated that the [2Fe‐2S]‐NsrR has a slightly higher binding affinity for its target DNA under reduced conditions than under oxidized conditions, indicating that NsrR may also regulate its transcriptional activity via the redox state of its iron‐sulfur cluster. This work was supported, in whole or in part, by the National Institute of Health Grant RO1 CA107494 from the United States Public Health Service. This work was also supported by the National Science Foundation Grant MCB‐0416 (to H.D.).