Chaperonins [1,2] are proteins involved in the folding of proteins or the assembly of oligomeric protein complexes. Their role seems to be to assist other polypeptides to maintain or assume conformations which permit their correct assembly into oligomeric structures. They are found in abundance in prokaryotes, chloroplasts and mitochondria. Chaperonins form oligomeric complexes and are composed of two different types of subunits: a 60 Kd protein, known as cpn60 (groEL in bacteria) and a 10 Kd protein, known as cpn10 (groES in bacteria).

The cpn60 protein shows weak ATPase activity and is a highly conserved protein of about 550 to 580 amino acid residues which has been described by different names in different species:

• Escherichia coli groEL protein, which is essential for the growth of the bacteria and the assembly of several bacteriophages.
• Cyanobacterial groEL analogues.
• Mycobacterium tuberculosis and leprae 65 Kd antigen, Coxiella burnetti heat shock protein B (gene htpB), Rickettsia tsutsugamushi major antigen 58, and Chlamydial 57 Kd hypersensitivity antigen (gene hypB).
• Chloroplast RuBisCO subunit binding-protein α and β chains, which bind ribulose bisphosphate carboxylase small and large subunits and are implicated in the assembly of the enzyme oligomer.
• Mammalian mitochondrial matrix protein P1 (mitonin or P60).
• Yeast HSP60 protein, a mitochondrial assembly factor.

As a signature pattern for these proteins, we have chosen a rather well conserved region of twelve residues, located in the last third of the cpn60 sequence.