title: Is the heme pocket region modulated by disulfide-bridge formation in fish and amphibian neuroglobins as in humans?
abstract: Neuroglobin, a globin characterized by a bis-histidine ligation of the heme iron, has been identified in mammalian and non-mammalian vertebrates, including fish, amphibians and reptiles. In human neuroglobin, the presence of an internal disulfide bond in the CD loop (CD7-D5) is found to modulate the ligand binding through a change in the heme pocket structure. Although the neuroglobin sequences mostly display conserved Cys at positions CD7, D5 and G18/19, a number of exceptions are known. In this study, neuroglobins from amphibian (Xenopus tropicalis) and fish (Chaenocephalus aceratus, Dissostichus mawsoni and Danio rerio) are investigated using electron paramagnetic resonance and optical absorption spectroscopy. All these neuroglobins differ from human neuroglobin in their Cys-positions. It is demonstrated that if disulfide bonds are formed in fish and amphibian neuroglobins, the reduction of these bonds does not result in alteration of the heme pocket in these globins. Furthermore, it is shown that mutagenesis of the Cys residues of X. tropicalis neuroglobin influences the protein structure. The amphibian neuroglobin is also found to be more resistant to H2O2-induced denaturation than the other neuroglobins under study, although all show an overall large stability in high concentrations of this oxidant. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.
authors: Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium. wendy.vanleuven@ua.ac.be
authors: Wendy
authors: W
authors: Van Leuven
authors: Bert
authors: B
authors: Cuypers
authors: Filip
authors: F
authors: Desmet
authors: Daniela
authors: D
authors: Giordano
authors: Cinzia
authors: C
authors: Verde
authors: Luc
authors: L
authors: Moens
authors: Sabine
authors: S
authors: Van Doorslaer
authors: Sylvia
authors: S
authors: Dewilde
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005399:Fishes / Q000378:metabolism; D005914:Globins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000078787:Neuroglobin; D011485:Protein Binding; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D014981:Xenopus / Q000378:metabolism
chemical_list: D004220:Disulfides; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D006418:Heme; D005914:Globins; D006861:Hydrogen Peroxide; D003545:Cysteine
keywords: EPR; Heme proteins; Neuroglobin; Protein structure