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- PDB-7oa6: Pseudo-atomic model for Hsp26 residues 63 to 214. Please be advis... -

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Database: PDB / ID: 7oa6
TitlePseudo-atomic model for Hsp26 residues 63 to 214. Please be advised that the target map is not of sufficient resolution to unambiguously position backbone or side chain atoms. This model represents a likely fit.
ComponentsHeat shock protein 26Heat shock response
KeywordsCHAPERONE / small heat shock proteins / Hsp26 S207E mutant
Function / homology
Function and homology information

cytoplasmic stress granule / unfolded protein binding / cellular response to heat / protein folding / mRNA binding / mitochondrion / identical protein binding / nucleus / cytoplasm
Similarity search - Function
: / Hsp20/alpha crystallin family / Small heat shock protein (sHSP) domain profile. / Alpha crystallin/Hsp20 domain / HSP20-like chaperone
Similarity search - Domain/homology
Heat shock protein 26
Similarity search - Component
Biological speciesSaccharomyces cerevisiae (baker's yeast)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 7.8 Å
AuthorsMuehlhofer, M. / Peters, C. / Kriehuber, T. / Kreuzeder, M. / Kazman, P. / Rodina, N. / Reif, B. / Haslbeck, M. / Weinkauf, S. / Buchner, J.
Funding support Germany, 1items
OrganizationGrant numberCountry
German Research Foundation (DFG)SFB 1035 Germany
CitationJournal: Nat Commun / Year: 2021
Title: Phosphorylation activates the yeast small heat shock protein Hsp26 by weakening domain contacts in the oligomer ensemble.
Authors: Moritz Mühlhofer / Carsten Peters / Thomas Kriehuber / Marina Kreuzeder / Pamina Kazman / Natalia Rodina / Bernd Reif / Martin Haslbeck / Sevil Weinkauf / Johannes Buchner /
Abstract: Hsp26 is a small heat shock protein (sHsp) from S. cerevisiae. Its chaperone activity is activated by oligomer dissociation at heat shock temperatures. Hsp26 contains 9 phosphorylation sites in ...Hsp26 is a small heat shock protein (sHsp) from S. cerevisiae. Its chaperone activity is activated by oligomer dissociation at heat shock temperatures. Hsp26 contains 9 phosphorylation sites in different structural elements. Our analysis of phospho-mimetic mutations shows that phosphorylation activates Hsp26 at permissive temperatures. The cryo-EM structure of the Hsp26 40mer revealed contacts between the conserved core domain of Hsp26 and the so-called thermosensor domain in the N-terminal part of the protein, which are targeted by phosphorylation. Furthermore, several phosphorylation sites in the C-terminal extension, which link subunits within the oligomer, are sensitive to the introduction of negative charges. In all cases, the intrinsic inhibition of chaperone activity is relieved and the N-terminal domain becomes accessible for substrate protein binding. The weakening of domain interactions within and between subunits by phosphorylation to activate the chaperone activity in response to proteotoxic stresses independent of heat stress could be a general regulation principle of sHsps.
DepositionApr 19, 2021Deposition site: PDBE / Processing site: PDBE
Revision 1.0Nov 24, 2021Provider: repository / Type: Initial release

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Deposited unit
A: Heat shock protein 26
B: Heat shock protein 26
I: Heat shock protein 26
J: Heat shock protein 26
X: Heat shock protein 26

Theoretical massNumber of molelcules
Total (without water)119,5535

  • Idetical with deposited unit
  • defined by author
  • Evidence: cross-linking
TypeNameSymmetry operationNumber
identity operation1_5551
Buried area13020 Å2
ΔGint-41 kcal/mol
Surface area32870 Å2


#1: Protein
Heat shock protein 26 / Heat shock response / 26 kDa heat shock protein

Mass: 23910.586 Da / Num. of mol.: 5
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (yeast)
Strain: ATCC 204508 / S288c / Gene: HSP26, YBR072W, YBR0714 / Plasmid: pQE60::HSP26 / Production host: Escherichia coli HB101 (bacteria) / References: UniProt: P15992

Experimental details


EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

Sample preparation

ComponentName: Top two rings (16 subunits) of a 40mer complex of Hsp26 mutant S207E. (use 0.487 as threshold to visualise)
Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT
Molecular weightValue: 0.382 MDa / Experimental value: NO
Source (natural)Organism: Saccharomyces cerevisiae (baker's yeast)
Source (recombinant)Organism: Escherichia coli (E. coli) / Strain: HB101 / Plasmid: pQE60::HSP26
Buffer solutionpH: 7.4
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationInstrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE-PROPANE / Humidity: 100 % / Chamber temperature: 294 K

Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: FEI TITAN KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELDBright-field microscopy / Nominal magnification: 105000 X / Nominal defocus max: 2800 nm / Nominal defocus min: 600 nm / Cs: 2.7 mm
Image recordingAverage exposure time: 8 sec. / Electron dose: 45 e/Å2 / Detector mode: COUNTING / Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Num. of real images: 5010
EM imaging opticsEnergyfilter name: GIF Quantum LS / Energyfilter slit width: 20 eV
Image scansMovie frames/image: 40


EM software
2SerialEMimage acquisition
4GctfCTF correction
7UCSF Chimeramodel fitting
9NAMDmodel refinement
10cryoSPARCinitial Euler assignment
11cryoSPARCfinal Euler assignment
13cryoSPARC3D reconstruction
Particle selectionNum. of particles selected: 688419
SymmetryPoint symmetry: C4 (4 fold cyclic)
3D reconstructionResolution: 7.8 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 375385 / Details: sharpened map / Symmetry type: POINT
Atomic model buildingProtocol: FLEXIBLE FIT / Space: REAL / Target criteria: Correlation coefficient
Details: Homology model generated with ITASSER with 1GME as template. Fitted with Chimera and flexibly fitted with NAMD. Residues 63 to 214 present in the model.

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