Direct Inhibition by Nitric Oxide of the Transcriptional Ferric Uptake Regulation Protein via Nitrosylation of the Iron

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 99; no. 26; pp. 16619 - 16624
• Main Authors: D'Autréaux, Benoît, Touati, Danièle, Bersch, Beate, Latour, Jean-Marc, Michaud-Soret, Isabelle
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.12.2002; National Acad Sciences
• Subjects: Aerobic conditions; Bacteria; Bacterial Proteins; Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - chemistry; Bacterial Proteins - physiology; Biochemistry; Biochemistry, Molecular Biology; Biological Sciences; Chelating agents; Deoxyribonucleic acid; Diethylamines; Dimerization; Dimers; DNA; E coli; Electron Spin Resonance Spectroscopy; Escherichia coli; Gene expression regulation; Iron; Iron - metabolism; Life Sciences; Ligands; Nitric Oxide; Nitric Oxide - physiology; Oxidative stress; Plasmids; Promoter regions; Protein Conformation; Proteins; Repressor Proteins; Repressor Proteins - antagonists & inhibitors; Repressor Proteins - chemistry; Repressor Proteins - physiology; Transcription, Genetic; metalloregulator; iron; nitric oxide; escherichia coli; transcription
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.252591299

Ferric uptake regulation protein (Fur) is a bacterial global regulator that uses iron as a cofactor to bind to specific DNA sequences. The function of Fur is not limited to iron homeostasis. A wide variety of genes involved in various mechanisms such as oxidative and acid stresses are under Fur control. Flavohemoglobin (Hmp) is an NO-detoxifying enzyme induced by NO and nitrosothiol compounds. Fur recently was found to regulate hmp in Salmonella typhimurium, and in Escherichia coli, the iron-chelating agent 2,2′-dipyridyl induces hmp expression. We now establish direct inhibition of E. coli Fur activity by NO. By using chromosomal Fur-regulated lacZ reporter fusion in E. coli, Fur activity is switched off by NO at micromolar concentration. In vitro Fur DNA-binding activity, as measured by protection of restriction site in aerobactin promoter, is directly sensitive to NO. NO reacts with FeIIin purified FeFur protein to form a S = 1/2 low-spin FeFur-NO complex with a g = 2.03 EPR signal. Appearance of the same EPR signal in NO-treated cells links nitrosylation of the iron with Fur inhibition. The nitrosylated Fur protein is still a dimer and is stable in anaerobiosis but slowly decays in air. This inhibition probably arises from a conformational switch, leading to an inactive dimeric protein. These data establish a link between control of iron metabolism and the response to NO effects.