Infrared spectroscopy provides insight into the role of dioxygen in the nitrosylation pathway of a [2Fe2S] cluster iron-sulfur protein.

Journal article

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 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: Grabarczyk, D; Ash, P; Vincent, K

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Chemical Society
• Journal: Journal of the American Chemical Society
• Volume: 136
• Issue: 32
• Pages: 11236-11239
• Publication date: 2014-07-31
• DOI: 10.1021/ja505291j
• EISSN: 1520-5126
• ISSN: 0002-7863
• Language: English
• Keywords: iodoacetamide; plant proteins; ferredoxins; hydrogen-ion concentration; nitric oxide; iron-sulfur proteins; iron; oxygen; SBTMR; nitroso compounds; spectrophotometry, Infrared; spinacia oleracea; cysteine; nitrogen