Multiple distinct assemblies reveal conformational flexibility in the small heat shock protein Hsp26.
Small heat shock proteins are a superfamily of molecular chaperones that suppress protein aggregation and provide protection from cell stress. A key issue for understanding their action is to define the interactions of subunit domains in these oligomeric assemblies. Cryo-electron microscopy of yeast Hsp26 reveals two distinct forms, each comprising 24 subunits arranged in a porous shell with tetrahedral symmetry. The subunits form elongated, asymmetric dimers that assemble via trimeric contacts. Modifications of both termini cause rearrangements that yield a further four assemblies. Each subunit contains an N-terminal region, a globular middle domain, the alpha-crystallin domain, and a C-terminal tail. Twelve of the C termini form 3-fold assembly contacts which are inserted into the interior of the shell, while the other 12 C termini form contacts on the surface. Hinge points between the domains allow a variety of assembly contacts, providing the flexibility required for formation of supercomplexes with non-native proteins.
White
Helen E
HE
Department of Crystallography, Birkbeck College, London WC1E 7HX, United Kingdom.
Orlova
Elena V
EV
Chen
Shaoxia
S
Wang
Luchun
L
Ignatiou
Athanasios
A
Gowen
Brent
B
Stromer
Thusnelda
T
Franzmann
Titus M
TM
Haslbeck
Martin
M
Buchner
Johannes
J
Saibil
Helen R
HR
D001665:Binding Sites; D020285:Cryoelectron Microscopy; D019281:Dimerization; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D020836:Protein Structure, Quaternary; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D038201:alpha-Crystallins / Q000737:chemistry
C499528:HSP26 protein, S cerevisiae; D006360:Heat-Shock Proteins; D029701:Saccharomyces cerevisiae Proteins; D038201:alpha-Crystallins