Prokaryotic and eukaryotic organisms respond to heat shock or other environmental stress by inducing the synthesis of proteins collectively known as heat-shock proteins (HSP) [1]. According to their molecular weight, HSPs are classified into several families such as HSP100, HSP90, HSP70, HSP60, and small HSPs (sHSPs) with molecular size ranging from 15 to 30 kDas [2,3,4,5,7,8]. These seem to act as chaperones that can protect other proteins against heat-induced denaturation and aggregation. sHSP proteins seem to form large heterooligomeric aggregates; their family is currently composed of the following members:

• Vertebrate heat shock protein HSP27 (HSP25), induced by a variety of environmental stresses.
• Drosophila heat shock proteins HSP22, HSP23, HSP26, HSP27, HSP67BA and BC.
• Caenorhabditis elegans HSP16 multigene family.
• Fungal HSP26 (budding yeast) and HSP30 (Neurospora crassa and Aspergillus Nidulans).
• Plant small HSP's. Plants have four classes of HSP20: classes I and II which are cytoplasmic, class III which is chloroplastic and class IV which is found in the endomembrane.
• α-crystallin A and B chains. α-crystallin is an abundant constituent of the eye lens of most vertebrate species. Its main function appears to be to maintain the correct refractive index of the lens. It is also found in other tissues where it seems to act as a chaperone [6].
• Schistosoma mansoni major egg antigen p40. Structurally, p40 is built of two tandem sHSP domains.
• A variety of prokaryotic proteins: ibpA and ibpB from Escherichia coli, hsp18 from Clostridium acetobutylicum, spore protein SP21 (HSPA) from Stigmatella aurantiaca, Mycobacterium leprae 18 Kd antigen and Mycobacterium tuberculosis 14 Kd antigen.
• Methanococcus jannaschii hypothetical protein MJ0285.

The sHSP family possess a conserved domain of approximately 80 to 100 amino acids. The sHSP domain forms a sandwich of two β-pleated sheets (see <PDB:2WJ5>) [6,7,8].

The profile we developed covers the entire sHSP domain.