Structure-function studies on small heat shock protein oligomeric assembly and interaction with unfolded polypeptides

J Biol Chem. 1997 Sep 26;272(39):24646-56. doi: 10.1074/jbc.272.39.24646.


The small heat shock protein (smHSP) and alpha-crystallin genes encode a family of 12-43-kDa proteins which assemble into large multimeric structures, function as chaperones by preventing protein aggregation, and contain a conserved region termed the alpha-crystallin domain. Here we report on the structural and functional characterization of Caenorhabditis elegans HSP16-2, a 16-kDa smHSP produced only under stress conditions. A combination of sedimentation velocity, size exclusion chromatography, and cross-linking analyses on wild-type HSP16-2 and five derivatives demonstrate that the N-terminal domain but not most of the the C-terminal extension which follows the alpha-crystallin domain is essential for the oligomerization of the smHSP into high molecular weight complexes. The N terminus of HSP16-2 is found to be buried within complexes which can accommodate at least an additional 4-kDa of heterologous sequence per subunit. Studies on the interaction of HSP16-2 with fluorescently-labeled and radiolabeled actin and tubulin reveal that this smHSP possesses a high affinity for unfolded intermediates which form early on the aggregation pathway, but has no apparent substrate specificity. Furthermore, both wild-type and C-terminally-truncated HSP16-2 can function as molecular chaperones by suppressing the thermally-induced aggregation of citrate synthase. Taken together, our data on HSP16-2 and a unique 12.6-kDa smHSP we have recently characterized demonstrate that multimerization is a prerequisite for the interaction of smHSPs with unfolded protein as well as for chaperone activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Amino Acid Sequence
  • Animals
  • Biopolymers
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins*
  • Citrate (si)-Synthase / metabolism
  • Heat-Shock Proteins / chemistry*
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Molecular Sequence Data
  • Mutagenesis
  • Protein Binding
  • Protein Conformation
  • Protein Denaturation
  • Protein Folding
  • Rabbits
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Substrate Specificity
  • Tubulin / metabolism


  • Actins
  • Biopolymers
  • Caenorhabditis elegans Proteins
  • Heat-Shock Proteins
  • Tubulin
  • hsp-16.2 protein, C elegans
  • Citrate (si)-Synthase