title: A distal ligand mutes the interaction of hydrogen sulfide with human neuroglobin.
abstract: Hydrogen sulfide is a critical signaling molecule, but high concentrations cause cellular toxicity. A four-enzyme pathway in the mitochondrion detoxifies H2S by converting it to thiosulfate and sulfate. Recent studies have shown that globins like hemoglobin and myoglobin can also oxidize H2S to thiosulfate and hydropolysulfides. Neuroglobin, a globin enriched in the brain, was reported to bind H2S tightly and was postulated to play a role in modulating neuronal sensitivity to H2S in conditions such as stroke. However, the H2S reactivity of the coordinately saturated heme in neuroglobin is expecteda priorito be substantially lower than that of the 5-coordinate hemes present in myoglobin and hemoglobin. To resolve this discrepancy, we explored the role of the distal histidine residue in muting the reactivity of human neuroglobin toward H2S. Ferric neuroglobin is slowly reduced by H2S and catalyzes its inefficient oxidative conversion to thiosulfate. Mutation of the distal His64residue to alanine promotes rapid binding of H2S and its efficient conversion to oxidized products. X-ray absorption, EPR, and resonance Raman spectroscopy highlight the chemically different reaction options influenced by the distal histidine ligand. This study provides mechanistic insights into how the distal heme ligand in neuroglobin caps its reactivity toward H2S and identifies by cryo-mass spectrometry a range of sulfide oxidation products with 2-6 catenated sulfur atoms with or without oxygen insertion, which accumulate in the absence of the His64ligand.
authors.affiliation: From the Department of Biological Chemistry and.
authors.forename: Markus
authors.initials: M
authors.lastname: Ruetz
authors.affiliation: the Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Jacques
authors.initials: J
authors.lastname: Kumutima
authors.affiliation: the Department of Pharmaceutical Science, Wayne State University, Detroit, Michigan 48201-2417.
authors.forename: Brianne E
authors.initials: BE
authors.lastname: Lewis
authors.affiliation: the University of Bordeaux, IBGC, UMR 5090, F33077 Bordeaux, France, and.|CNRS, Institute of Biochemistry and Cellular Genetics, UMR 5095, F33077 Bordeaux, France.
authors.forename: Milos R
authors.initials: MR
authors.lastname: Filipovic
authors.affiliation: the Departments of Chemistry and Biophysics, University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Lehnert
authors.affiliation: the Department of Pharmaceutical Science, Wayne State University, Detroit, Michigan 48201-2417.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Stemmler
authors.affiliation: From the Department of Biological Chemistry and rbanerje@umich.edu.
authors.forename: Ruma
authors.initials: R
authors.lastname: Banerjee
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005914:Globins / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D006801:Humans; D006862:Hydrogen Sulfide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D013058:Mass Spectrometry; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D000078787:Neuroglobin; D010100:Oxygen / Q000737:chemistry; D011487:Protein Conformation; D021241:Spectrometry, Mass, Electrospray Ionization; D013059:Spectrum Analysis, Raman; D013440:Sulfides / Q000737:chemistry; D013885:Thiosulfates / Q000737:chemistry; D013917:Thrombin / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D008024:Ligands; D009211:Myoglobin; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D013440:Sulfides; D013885:Thiosulfates; D006418:Heme; D006639:Histidine; D005914:Globins; D013917:Thrombin; D003545:Cysteine; D010100:Oxygen; D006862:Hydrogen Sulfide
keywords: Raman spectroscopy; X-ray absorption spectroscopy; globin; heme; hydrogen sulfide; neuroglobin; spectroscopy