Sulfolobus shibatae is a hyperthermophilic archaeon that was first identified living in acidic geothermal hot springs. This organism grows optimally at pH 3.0-4.0 and 83°C (1), however it grows over the temperature range of 7585 °C. When S. shibatae is subjected to higher temperatures (85-90°C) a heatshock response is observed and the major protein induced is a large ring structure TF55 (2), also called archaeosome (3) or rosettasome (4), which is composed of two different subunits (4), designated α and β (3 4)). Apart from the presence of two subunits, another difference between this molecule and the prokaryotic GroEL is the number of subunits per ring. In S. shibatae, nine subunits form each ring compared with seven in GroEL.