title: Reductive nitrosylation of Methanosarcina acetivorans protoglobin: a comparative study.
abstract: Methanosarcina acetivorans is a strictly anaerobic non-motile methane-producing Archaea expressing protoglobin (Pgb) which might either facilitate O(2) detoxification or act as a CO sensor/supplier in methanogenesis. Unusually, M. acetivorans Pgb (MaPgb) binds preferentially O(2) rather than CO and displays anticooperativity in ligand binding. Here, kinetics and/or thermodynamics of ferric and ferrous MaPgb (MaPgb(III) and MaPgb(II), respectively) nitrosylation are reported. Data were obtained between pH 7.2 and 9.5, at 22.0 °C. Addition of NO to MaPgb(III) leads to the transient formation of MaPgb(III)-NO in equilibrium with MaPgb(II)-NO(+). In turn, MaPgb(II)-NO(+) is converted to MaPgb(II) by OH(-)-based catalysis. Then, MaPgb(II) binds NO very rapidly leading to MaPgb(II)-NO. The rate-limiting step for reductive nitrosylation of MaPgb(III) is represented by the OH(-)-mediated reduction of MaPgb(II)-NO(+) to MaPgb(II). Present results highlight the potential role of MaPgb in scavenging of reactive nitrogen and oxygen species.
authors.affiliation: Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Via della Vasca Navale 79, I-00146 Roma, Italy. ascenzi@uniroma3.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pesce
authors.forename: Marco
authors.initials: M
authors.lastname: Nardini
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Chiara
authors.initials: C
authors.lastname: Ciaccio
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
authors.forename: Sylvia
authors.initials: S
authors.lastname: Dewilde
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005914:Globins / Q000737:chemistry*; D007700:Kinetics; D017020:Methanosarcina / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry*; D026361:Reactive Nitrogen Species / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D019843:Archaeal Proteins; D005290:Ferric Compounds; D005296:Ferrous Compounds; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D005914:Globins; D009584:Nitrogen