Small heat shock proteins from extremophiles: a review

Extremophiles. 2004 Feb;8(1):1-11. doi: 10.1007/s00792-003-0362-3. Epub 2003 Nov 19.


Many microorganisms from extreme environments have been well characterized, and increasing access to genomic sequence data has recently allowed the analysis of the protein families related to stress responses. Heat shock proteins appear to be ubiquitous in extremophiles. In this review, we focus on the family of small heat shock proteins (sHSPs) from extremophiles, which are alpha-crystallin homologues. Like the alpha-crystallin eye lens proteins, sHSPs act as molecular chaperones and prevent aggregation of denatured proteins under heat and desiccation stress. Many putative sHSP homologues have been identified in the genomic sequences of all classes of extremophiles. Current studies of shsp gene expression have revealed mechanisms of regulation and activity distinct from other known hsp gene regulation systems. Biochemical studies on sHSPs are limited to thermophilic and hyperthermophilic organisms, and the only two available crystal structures of sHSPs from Methanocaldococcus jannaschii, a hyperthermophilic archaeon and a mesophilic eukaryote, have contributed significantly to an understanding of the mechanisms of action of sHSPs, although many aspects remain unclear.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Archaeal Proteins / chemistry
  • Archaeal Proteins / genetics
  • Archaeal Proteins / physiology
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology
  • Eukaryotic Cells
  • Gene Expression Regulation
  • Genomics
  • Heat-Shock Proteins / chemistry*
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / physiology
  • Humans
  • Models, Molecular
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / genetics
  • Molecular Chaperones / physiology
  • Molecular Sequence Data
  • Molecular Structure
  • Proteomics
  • Sequence Homology, Amino Acid
  • alpha-Crystallins / chemistry
  • alpha-Crystallins / genetics
  • alpha-Crystallins / physiology


  • Archaeal Proteins
  • Bacterial Proteins
  • Heat-Shock Proteins
  • Molecular Chaperones
  • alpha-Crystallins