Solid-state NMR and SAXS studies provide a structural basis for the activation of alphaB-crystallin oligomers.
The small heat shock protein alphaB-crystallin (alphaB) contributes to cellular protection against stress. For decades, high-resolution structural studies on oligomeric alphaB have been confounded by its polydisperse nature. Here, we present a structural basis of oligomer assembly and activation of the chaperone using solid-state NMR and small-angle X-ray scattering (SAXS). The basic building block is a curved dimer, with an angle of approximately 121 degrees between the planes of the beta-sandwich formed by alpha-crystallin domains. The highly conserved IXI motif covers a substrate binding site at pH 7.5. We observe a pH-dependent modulation of the interaction of the IXI motif with beta4 and beta8, consistent with a pH-dependent regulation of the chaperone function. N-terminal region residues Ser59-Trp60-Phe61 are involved in intermolecular interaction with beta3. Intermolecular restraints from NMR and volumetric restraints from SAXS were combined to calculate a model of a 24-subunit alphaB oligomer with tetrahedral symmetry.
Jehle
Stefan
S
Leibniz-Institut Für Molekulare Pharmakologie, Berlin, Germany.
Rajagopal
Ponni
P
Bardiaux
Benjamin
B
Markovic
Stefan
S
Kühne
Ronald
R
Stout
Joseph R
JR
Higman
Victoria A
VA
Klevit
Rachel E
RE
van Rossum
Barth-Jan
BJ
Oschkinat
Hartmut
H
D001665:Binding Sites; D002623:Chemistry Techniques, Analytical; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D020836:Protein Structure, Quaternary; D038203:alpha-Crystallin B Chain / Q000737:chemistry*
D038203:alpha-Crystallin B Chain
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