title: The oligomer plasticity of the small heat-shock protein Lo18 from Oenococcus oeni influences its role in both membrane stabilization and protein protection.
abstract: The ability of the small Hsp (heat-shock protein) Lo18 from Oenococcus oeni to modulate the membrane fluidity of liposomes or to reduce the thermal aggregation of proteins was studied as a function of the pH in the range 5-9. We have determined by size-exclusion chromatography and analytical ultracentrifugation that Lo18 assembles essentially as a 16-mer at acidic pH. Its quaternary structure evolves to a mixture of lower molecular mass oligomers probably in dynamic equilibrium when the pH increases. The best Lo18 activities are observed at pH 7 when the particle distribution contains a major proportion of dodecamers. At basic pH, particles corresponding to a dimer prevail and are thought to be the building blocks leading to oligomerization of Lo18. At acidic pH, the dimers are organized in a double-ring of stacked octamers to form the 16-mer as shown by the low-resolution structure determined by electron microscopy. Experiments performed with a modified protein (A123S) shown to preferentially form dimers confirm these results. The α-crystallin domain of Methanococcus jannaschii Hsp16.5, taken as a model of the Lo18 counterpart, fits with the electron microscopy envelope of Lo18.
authors.affiliation: UMR PAM-équipe VALMIS, IUVV, Dijon, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Maitre
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Weidmann
authors.forename: Aurélie
authors.initials: A
authors.lastname: Rieu
authors.forename: Daphna
authors.initials: D
authors.lastname: Fenel
authors.forename: Guy
authors.initials: G
authors.lastname: Schoehn
authors.forename: Christine
authors.initials: C
authors.lastname: Ebel
authors.forename: Jacques
authors.initials: J
authors.lastname: Coves
authors.forename: Jean
authors.initials: J
authors.lastname: Guzzo
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry; D008560:Membrane Fluidity; D056585:Oenococcus / Q000378:metabolism*; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D038201:alpha-Crystallins / Q000737:chemistry
chemical_list: D019843:Archaeal Proteins; C113795:HSP16.5 protein, Methanococcus jannaschii; D006360:Heat-Shock Proteins; D008081:Liposomes; D038201:alpha-Crystallins