Essential structural and functional features of small heat shock proteins in molecular chaperoning process.

Small heat shock proteins are ubiquitously found in all three domains of life, although they are the most poorly conserved family of molecular chaperones. Their involvement in anti-stress mechanisms of the cells have been clearly demonstrated by induction of their expression in response to various environmental and pathological stresses. Small heat shock proteins comprise the most effective chaperone family concerning their unusual capacity of substrate binding. It is well documented that small heat shock proteins associate with unfolding substrate proteins and form large oligomeric complexes to prevent their aggregation and accumulation, that otherwise would impair the normal cell functions. The substrates captured by small heat shock proteins are further refolded to their native state by ATP depended chaperones. During heat stress, the induced expression and activation of the small heat shock proteins, might reflect that this mechanism of protein quality control contributes to acquired thermotolerance in hyperthermophilic archaea, as well.