Quaternary dynamics and plasticity underlie small heat shock protein chaperone function.
Small Heat Shock Proteins (sHSPs) are a diverse family of molecular chaperones that prevent protein aggregation by binding clients destabilized during cellular stress. Here we probe the architecture and dynamics of complexes formed between an oligomeric sHSP and client by employing unique mass spectrometry strategies. We observe over 300 different stoichiometries of interaction, demonstrating that an ensemble of structures underlies the protection these chaperones confer to unfolding clients. This astonishing heterogeneity not only makes the system quite distinct in behavior to ATP-dependent chaperones, but also renders it intractable by conventional structural biology approaches. We find that thermally regulated quaternary dynamics of the sHSP establish and maintain the plasticity of the system. This extends the paradigm that intrinsic dynamics are crucial to protein function to include equilibrium fluctuations in quaternary structure, and suggests they are integral to the sHSPs' role in the cellular protein homeostasis network.
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Florian
F
Stengel
Andrew J
AJ
Baldwin
Alexander J
AJ
Painter
Nomalie
N
Jaya
Eman
E
Basha
Lewis E
LE
Kay
Elizabeth
E
Vierling
Carol V
CV
Robinson
Justin L P
JL
Benesch
D055592:Biophysical Phenomena; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism; D050888:Heat-Shock Proteins, Small / Q000737:chemistry* / Q000378:metabolism*; D049409:Luciferases, Firefly / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D046912:Multiprotein Complexes; D018532:Pisum sativum / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D013816:Thermodynamics
C489905:HSP18 protein, plant; D006360:Heat-Shock Proteins; D050888:Heat-Shock Proteins, Small; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D010940:Plant Proteins; D011994:Recombinant Proteins; C485197:luciferase, Photinus; D049409:Luciferases, Firefly