title: Novel dissociation mechanism of a polychaetous annelid extracellular haemoglobin.
abstract: The extracellular haemoglobin of the marine polychaete, Arenicola marina, is a hexagonal bilayer haemoglobin of approximately 3600 kDa, formed by the covalent and noncovalent association of many copies of both globin subunits (monomer and trimer) and nonglobin or 'linker' subunits. In order to analyse the interactions between globin and linker subunits, dissociation and reassociation experiments were carried out under whereby Arenicola hexagonal bilayer haemoglobin was exposed to urea and alkaline pH and the effect was followed by gel filtration, SDS/PAGE, UV-visible spectrophotometry, electrospray-ionization MS, multiangle laser light scattering and transmission electron microscopy. The analysis of Arenicola haemoglobin dissociation indicates a novel and complex mechanism of dissociation compared with other annelid extracellular haemoglobins studied to date. Even though the chemically induced dissociation triggers partial degradation of some subunits, spontaneous reassociation was observed, to some extent. Parallel dissociation of Lumbricus haemoglobin under similar conditions shows striking differences that allow us to propose a hypothesis on the nature of the intersubunit contacts that are essential to form and to hold such a complex quaternary structure.
authors.affiliation: Equipe Ecophysiologie: Adaptation et Evolution Moléculaires, UMR 7144, CNRS-UPMC, Station Biologique, 29682 Roscoff, France. rousselo@sb-roscoff.fr
authors.forename: Morgane
authors.initials: M
authors.lastname: Rousselot
authors.forename: Dominique
authors.initials: D
authors.lastname: Le Guen
authors.forename: Christine
authors.initials: C
authors.lastname: Chabasse
authors.forename: Franck
authors.initials: F
authors.lastname: Zal
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000737:chemistry; D002850:Chromatography, Gel; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D011077:Polychaeta / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002413:Cations, Divalent; D006454:Hemoglobins; D021122:Protein Subunits