Biochemical and biophysical characterization of the Mg2+-induced 90-kDa heat shock protein oligomers.
The 90-kDa heat shock protein (Hsp90) is involved in the regulation and activation of numerous client proteins essential for diverse functions such as cell growth and differentiation. Although the function of cytosolic Hsp90 is dependent on a battery of cochaperone proteins regulating both its ATPase activity and its interaction with client proteins, little is known about the real Hsp90 molecular mechanism. Besides its highly flexible dimeric state, Hsp90 is able to self-oligomerize in the presence of divalent cations or under heat shock. In addition to dimers, oligomers exhibit a chaperone activity. In this work, we focused on Mg(2+)-induced oligomers that we named Type I, Type II, and Type III in increasing molecular mass order. After stabilization of these quaternary structures, we optimized a purification protocol. Combining analytical ultracentrifugation, size exclusion chromatography coupled to multiangle laser light scattering, and high mass matrix-assisted laser desorption/ionization time of flight mass spectrometry, we determined biochemical and biophysical characteristics of each Hsp90 oligomer. We demonstrate that Type I oligomer is a tetramer, and Type II is an hexamer, whereas Type III is a dodecamer. These even-numbered structures demonstrate that the building brick for oligomerization is the dimer up to the Type II, whereas Type III probably results from the association of two Type II. Moreover, the Type II oligomer structure, studied by negative stain transmission electron microscopy tomography, exhibits a "nest-like" shape that forms a "cozy chaperoning chamber" where the client protein folding/protection could occur.
Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Université de Rennes 1, 35042 Rennes Cedex France.
Laura
L
Moullintraffort
Equipe Ecophysiologie des Invertébrés Marins des Milieux Extrêmes, Université Pierre et Marie Curie Paris VI, CNRS UMR 7144, Station Biologique de Roscoff, B.P. 74, 29682 Roscoff, France.
Matthieu
M
Bruneaux
CovalX AG, 8952 Zürich-Schlieren, Switzerland.
Alexis
A
Nazabal
CRO2 UMR Inserm 911, Université de la Méditerranée, Faculté de Pharmacie, 13385 Marseille Cedex 5, France.
Diane
D
Allegro
Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Université de Rennes 1, 35042 Rennes Cedex France.
Emmanuel
E
Giudice
Equipe Ecophysiologie des Invertébrés Marins des Milieux Extrêmes, Université Pierre et Marie Curie Paris VI, CNRS UMR 7144, Station Biologique de Roscoff, B.P. 74, 29682 Roscoff, France.
Franck
F
Zal
CRO2 UMR Inserm 911, Université de la Méditerranée, Faculté de Pharmacie, 13385 Marseille Cedex 5, France.
Vincent
V
Peyrot
CovalX AG, 8952 Zürich-Schlieren, Switzerland.
Pascale
P
Barbier
Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Université de Rennes 1, 35042 Rennes Cedex France.
Daniel
D
Thomas
Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Université de Rennes 1, 35042 Rennes Cedex France. Electronic address: cyrille.garnier@univ-rennes1.fr.
Cyrille
C
Garnier
D000818:Animals; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013552:Swine; D014461:Ultracentrifugation
D001704:Biopolymers; D018841:HSP90 Heat-Shock Proteins; D008274:Magnesium