title: [FeFe]-hydrogenase oxygen inactivation is initiated at the H cluster 2Fe subcluster.
abstract: The [FeFe]-hydrogenase catalytic site H cluster is a complex iron sulfur cofactor that is sensitive to oxygen (O2). The O2 sensitivity is a significant barrier for production of hydrogen as an energy source in water-splitting, oxygenic systems. Oxygen reacts directly with the H cluster, which results in rapid enzyme inactivation and eventual degradation. To investigate the progression of O2-dependent [FeFe]-hydrogenase inactivation and the process of H cluster degradation, the highly O2-sensitive [FeFe]-hydrogenase HydA1 from the green algae Chlamydomonas reinhardtii was exposed to defined concentrations of O2 while monitoring the loss of activity and accompanying changes in H cluster spectroscopic properties. The results indicate that H cluster degradation proceeds through a series of reactions, the extent of which depend on the initial enzyme reduction/oxidation state. The degradation process begins with O2 interacting and reacting with the 2Fe subcluster, leading to degradation of the 2Fe subcluster and leaving an inactive [4Fe-4S] subcluster state. This final inactive degradation product could be reactivated in vitro by incubation with 2Fe subcluster maturation machinery, specifically HydF(EG), which was observed by recovery of enzyme activity.
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Swanson
authors.forename: Michael W
authors.initials: MW
authors.lastname: Ratzloff
authors.forename: David W
authors.initials: DW
authors.lastname: Mulder
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Artz
authors.forename: Shourjo
authors.initials: S
authors.lastname: Ghose
authors.forename: Andrew
authors.initials: A
authors.lastname: Hoffman
authors.forename: Spencer
authors.initials: S
authors.lastname: White
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Zadvornyy
authors.forename: Joan B
authors.initials: JB
authors.lastname: Broderick
authors.forename: Brian
authors.initials: B
authors.lastname: Bothner
authors.forename: Paul W
authors.initials: PW
authors.lastname: King
authors.forename: John W
authors.initials: JW
authors.lastname: Peters
mesh_terms: D002248:Carbon Monoxide / Q000494:pharmacology; D016825:Chlamydomonas reinhardtii / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006859:Hydrogen / Q000737:chemistry* / Q000378:metabolism; D006864:Hydrogenase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology*; D011487:Protein Conformation
chemical_list: D004791:Enzyme Inhibitors; D002248:Carbon Monoxide; D006859:Hydrogen; D007501:Iron; D006864:Hydrogenase; D010100:Oxygen