title: Electron transfer function versus oxygen delivery: a comparative study for several hexacoordinated globins across the animal kingdom.
abstract: Caenorhabditis elegans globin GLB-26 (expressed from gene T22C1.2) has been studied in comparison with human neuroglobin (Ngb) and cytoglobin (Cygb) for its electron transfer properties. GLB-26 exhibits no reversible binding for O(2) and a relatively low CO affinity compared to myoglobin-like globins. These differences arise from its mechanism of gaseous ligand binding since the heme iron of GLB-26 is strongly hexacoordinated in the absence of external ligands; the replacement of this internal ligand, probably the E7 distal histidine, is required before binding of CO or O(2) as for Ngb and Cygb. Interestingly the ferrous bis-histidyl GLB-26 and Ngb, another strongly hexacoordinated globin, can transfer an electron to cytochrome c (Cyt-c) at a high bimolecular rate, comparable to those of inter-protein electron transfer in mitochondria. In addition, GLB-26 displays an unexpectedly rapid oxidation of the ferrous His-Fe-His complex without O(2) actually binding to the iron atom, since the heme is oxidized by O(2) faster than the time for distal histidine dissociation. These efficient mechanisms for electron transfer could indicate a family of hexacoordinated globin which are functionally different from that of pentacoordinated globins.
authors.affiliation: INSERM U779, Universities Paris VI and XI, Le Kremlin-Bicêtre, France. Laurent.Kiger@inserm.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Kiger
authors.forename: Lesley
authors.initials: L
authors.lastname: Tilleman
authors.forename: Eva
authors.initials: E
authors.lastname: Geuens
authors.forename: David
authors.initials: D
authors.lastname: Hoogewijs
authors.forename: Christophe
authors.initials: C
authors.lastname: Lechauve
authors.forename: Luc
authors.initials: L
authors.lastname: Moens
authors.forename: Sylvia
authors.initials: S
authors.lastname: Dewilde
authors.forename: Michael C
authors.initials: MC
authors.lastname: Marden
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D000078842:Cytoglobin; D004579:Electron Transport; D005914:Globins / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D006639:Histidine; D006801:Humans; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D000078787:Neuroglobin; D010100:Oxygen / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: C000627265:CYGB protein, human; D029742:Caenorhabditis elegans Proteins; D000078842:Cytoglobin; C549787:GLB-26 protein, C elegans; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D006418:Heme; D006639:Histidine; D002248:Carbon Monoxide; D005914:Globins; D045304:Cytochromes c; D007501:Iron; D010100:Oxygen