期刊
BIOCHEMISTRY
卷 39, 期 2, 页码 388-396出版社
AMER CHEMICAL SOC
DOI: 10.1021/bi991378g
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资金
- NHLBI NIH HHS [HL54762] Funding Source: Medline
- NIGMS NIH HHS [GM33576, GM53228] Funding Source: Medline
Electronic absorption, EPR, and resonance Raman spectroscopies revealed that CooA, the GO-sensing transcriptional regulator from Rhodospirillum rubrum, reacts with NO to form a five-coordinate NO-heme. NO must therefore displace both of the heme ligands from six-coordinate, low-spin Fe(II)CooA in forming five-coordinate Fe(II)CooA(NO). CO in contrast, displaces a single heme ligand from Fe(II)CooA to form six-coordinate Fe(II)CooA(CO). Of a series of common heme-binding ligands, only CO and NO were able to bind to the heme of wild-type CooA; imidazole, azide anion, and cyanide anion had no effect on the heme absorption spectrum. Although NO binds to the heme and displaces the endogenous ligands, NO was not able to induce CooA to bind to its target DNA. The mechanism of GO-dependent activation of CooA is thus more complex than simple displacement of a ligand from the heme iron since NO does not trigger DNA binding. These observations suggest that the CooA heme site discriminates between NO and the biologically relevant signal, CO.
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