title: Conversion of a heme-based oxygen sensor to a heme oxygenase by hydrogen sulfide: effects of mutations in the heme distal side of a heme-based oxygen sensor phosphodiesterase (Ec DOS).
abstract: The heme-based oxygen-sensor phosphodiesterase from Escherichia coli (Ec DOS), is composed of an N-terminal heme-bound oxygen sensing domain and a C-terminal catalytic domain. Oxygen (O2) binding to the heme Fe(II) complex in Ec DOS substantially enhances catalysis. Addition of hydrogen sulfide (H2S) to the heme Fe(III) complex in Ec DOS also remarkably stimulates catalysis in part due to the heme Fe(III)-SH and heme Fe(II)-O2 complexes formed by H2S. In this study, we examined the roles of the heme distal amino acids, M95 (the axial ligand of the heme Fe(II) complex) and R97 (the O2 binding site in the heme Fe(II)-O2 complex) of the isolated heme-binding domain of Ec DOS (Ec DOS-PAS) in the binding of H2S under aerobic conditions. Interestingly, R97A and R97I mutant proteins formed an oxygen-incorporated modified heme, verdoheme, following addition of H2S combined with H2O2 generated by the reactions. Time-dependent mass spectroscopic data corroborated the findings. In contrast, H2S did not interact with the heme Fe(III) complex of M95H and R97E mutants. Thus, M95 and/or R97 on the heme distal side in Ec DOS-PAS significantly contribute to the interaction of H2S with the Fe(III) heme complex and also to the modification of the heme Fe(III) complex with reactive oxygen species. Importantly, mutations of the O2 binding site of the heme protein converted its function from oxygen sensor to that of a heme oxygenase. This study establishes the novel role of H2S in modifying the heme iron complex to form verdoheme with the aid of reactive oxygen species.
authors.affiliation: Department of Cell Biology, Shantou University Medical College, 22 Xinling Road, Shantou, 515041, Guangdong, China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Du
authors.forename: Gefei
authors.initials: G
authors.lastname: Liu
authors.forename: Yinxia
authors.initials: Y
authors.lastname: Yan
authors.forename: Dongyang
authors.initials: D
authors.lastname: Huang
authors.forename: Wenhong
authors.initials: W
authors.lastname: Luo
authors.forename: Marketa
authors.initials: M
authors.lastname: Martinkova
authors.forename: Petr
authors.initials: P
authors.lastname: Man
authors.forename: Toru
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D055162:Biocatalysis; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D009154:Mutation; D010100:Oxygen / Q000032:analysis* / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D005290:Ferric Compounds; D017382:Reactive Oxygen Species; D006418:Heme; D006861:Hydrogen Peroxide; D006419:Heme Oxygenase (Decyclizing); D010727:Phosphoric Diester Hydrolases; D010100:Oxygen; D006862:Hydrogen Sulfide