title: Globin-like proteins in Caenorhabditis elegans: in vivo localization, ligand binding and structural properties.
abstract: BACKGROUND
  The genome of the nematode Caenorhabditis elegans contains more than 30 putative globin genes that all are transcribed. Although their translated amino acid sequences fit the globin fold, a variety of amino-acid substitutions and extensions generate a wide structural diversity among the putative globins. No information is available on the physicochemical properties and the in vivo expression.
  
  
  RESULTS
  We expressed the globins in a bacterial system, characterized the purified proteins by optical and resonance Raman spectroscopy, measured the kinetics and equilibria of O2 binding and determined the crystal structure of GLB-1* (CysGH2 --> Ser mutant). Furthermore, we studied the expression patterns of glb-1 (ZK637.13) and glb-26 (T22C1.2) in the worms using green fluorescent protein technology and measured alterations of their transcript abundances under hypoxic conditions.GLB-1* displays the classical three-over-three alpha-helical sandwich of vertebrate globins, assembled in a homodimer associated through facing E- and F-helices. Within the heme pocket the dioxygen molecule is stabilized by a hydrogen bonded network including TyrB10 and GlnE7.GLB-1 exhibits high ligand affinity, which is, however, lower than in other globins with the same distal TyrB10-GlnE7 amino-acid pair. In the absence of external ligands, the heme ferrous iron of GLB-26 is strongly hexacoordinated with HisE7, which could explain its extremely low affinity for CO. This globin oxidizes instantly to the ferric form in the presence of oxygen and is therefore incapable of reversible oxygen binding.
  
  
  CONCLUSIONS
  The presented data indicate that GLB-1 and GLB-26 belong to two functionally-different globin classes.
authors.affiliation: Department of Biomedical Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors.forename: Eva
authors.initials: E
authors.lastname: Geuens
authors.forename: David
authors.initials: D
authors.lastname: Hoogewijs
authors.forename: Marco
authors.initials: M
authors.lastname: Nardini
authors.forename: Evi
authors.initials: E
authors.lastname: Vinck
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pesce
authors.forename: Laurent
authors.initials: L
authors.lastname: Kiger
authors.forename: Angela
authors.initials: A
authors.lastname: Fago
authors.forename: Lesley
authors.initials: L
authors.lastname: Tilleman
authors.forename: Sasha
authors.initials: S
authors.lastname: De Henau
authors.forename: Michael C
authors.initials: MC
authors.lastname: Marden
authors.forename: Roy E
authors.initials: RE
authors.lastname: Weber
authors.forename: Sabine
authors.initials: S
authors.lastname: Van Doorslaer
authors.forename: Jacques
authors.initials: J
authors.lastname: Vanfleteren
authors.forename: Luc
authors.initials: L
authors.lastname: Moens
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Sylvia
authors.initials: S
authors.lastname: Dewilde
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D005914:Globins / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D013059:Spectrum Analysis, Raman
chemical_list: D029742:Caenorhabditis elegans Proteins; C549786:GLB-1 protein, C elegans; C549787:GLB-26 protein, C elegans; D008024:Ligands; D005914:Globins; D010100:Oxygen