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Nat Struct Mol Biol. 2010 Sep;17(9):1037-42. doi: 10.1038/nsmb.1891. Epub 2010 Aug 29.

Solid-state NMR and SAXS studies provide a structural basis for the activation of alphaB-crystallin oligomers.

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  • 1Leibniz-Institut Für Molekulare Pharmakologie, Berlin, Germany.

Abstract

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.

PMID:
20802487
[PubMed - indexed for MEDLINE]
PMCID:
PMC2957905
Free PMC Article
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