title: Infrared spectroscopy provides insight into the role of dioxygen in the nitrosylation pathway of a [2Fe2S] cluster iron-sulfur protein.
abstract: We use infrared spectroscopy to demonstrate the critical role that trace O2 plays in determining the products formed when a [2Fe2S] cluster protein reacts with nitric oxide (NO). The observed importance of O2 may have physiological relevance, as many pathogens sense NO using iron-sulfur proteins and will be exposed to NO in an aerobic environment during a mammalian immune response. We show that the [2Fe2S]-containing spinach ferredoxin I undergoes reaction with NO at pH 6.0, with the proportion of protein-bound Roussin's Red Ester compared to the dinitrosyl iron complex product favored by trace O2. Roussin's Red Ester is also favored on nitrosylation in the presence of the thiolate scavenging reagent, iodoacetamide, suggesting that the role of O2 is in oxidative sequestration of cysteine thiolates. Infrared spectroscopy has been overlooked as a tool for studying iron-sulfur protein nitrosylation despite the fact that there exists a wealth of infrared spectroscopic data on small-molecule nitrosyl clusters which serve as models for the identification of protein-bound nitrosyl clusters.
authors: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K.
authors: Daniel B
authors: DB
authors: Grabarczyk
authors: Philip A
authors: PA
authors: Ash
authors: Kylie A
authors: KA
authors: Vincent
mesh_terms: D003545:Cysteine / Q000737:chemistry; D005288:Ferredoxins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007460:Iodoacetamide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D009603:Nitroso Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D018724:Spinacia oleracea / Q000737:chemistry
chemical_list: D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D009603:Nitroso Compounds; D010940:Plant Proteins; C028357:Roussin red methyl ester; D009569:Nitric Oxide; D007501:Iron; D003545:Cysteine; D009584:Nitrogen; D010100:Oxygen; D007460:Iodoacetamide