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

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

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding Sites
  • Chemistry Techniques, Analytical
  • Humans
  • Hydrogen-Ion Concentration
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Quaternary*
  • alpha-Crystallin B Chain / chemistry*

Substances

  • alpha-Crystallin B Chain

Associated data

  • PDB/2KLR