TAILIEUCHUNG - Báo cáo khoa học: Novel dissociation mechanism of a polychaetous annelid extracellular haemoglobin

The extracellular haemoglobin of the marine polychaete,Arenicola marina, is a hexagonal bilayer haemoglobin of 3600 kDa, formed by the covalent and noncovalent association of many copies of both globin subunits (monomer and trimer) and nonglobin or ‘linker’ subunits. | iFEBS Journal Novel dissociation mechanism of a polychaetous annelid extracellular haemoglobin Morgane Rousselot Dominique Le Guen Christine Chabasse and Franck Zal Equipe Ecophysiologie Adaptation et Evolution Moleculaires UMR 7144 CNRS-UPMC Station Biologique 29682 Roscoff France Keywords dissociation ESI-MS hemoglobin MALLS polychaete Correspondence M. Rousselot Place Georges Teissier BP 74 29682 Roscoff Cedex France Fax 33 298292324 Tel 33 298292323 E-mail rousselo@ Received 30 November 2005 revised 18 January 2006 accepted 23 January 2006 doi The extracellular haemoglobin of the marine polychaete Arenicola marina is a hexagonal bilayer haemoglobin of w 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. The giant extracellular hexagonal bilayer haemoglobins HBL-Hbs found in most terrestrial aquatic shallowwater and deep-sea annelids including .

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