A REVIEW OF ACQUIRED THERMOTOLERANCE, HEAT-SHOCK PROTEINS, AND MOLECULAR CHAPERONES IN ARCHAEA

Acquired thermotolerance, the associated synthesis of heat-shock prote ins (HSPs) under stress conditions, and the role of HSPs as molecular chaperones under normal growth conditions have been studied extensivel y in eukaryotes and bacteria, whereas research in these areas in archa ea is only beginning. All organisms have evolved a variety of strategi es for coping with high-temperature stress, and among these strategies is the increased synthesis of HSPs. The facts that both high temperat ures and chemical stresses induce the HSPs and that some of the HSPs r ecognize and bind to unfolded proteins in vitro have led to the theory that the function of HSPs is to prevent protein aggregation in vivo. The facts that some HSPs are abundant under normal growth conditions a nd that they assist in protein folding in vitro have led to the theory that they assist protein folding in vivo, in this role, they are refe rred to as molecular chaperones. The limited research on acquired ther motolerance, HSPs, and molecular chaperones in archaea, particularly t he hyperthermophilic archaea, suggests that these extremophiles provid e a new perspective in these areas of research, both because they are members of a separate phylogenetic domain and because they have evolve d to live under extreme conditions.