Posttranslational modulation on the biological activities of molecular chaperones.

Molecular chaperones are a family of proteins that were first noticed to exist about 45 years ago from their increased transcription under heat shock conditions. As a result, the regulation of their encoding genes has been subject to extensive studies. Recent studies revealed that the biological activities of molecular chaperones can also be effectively modulated at the protein level. The ways of modulation so far elucidated include allosteric effect, covalent modification, protein-protein interaction, and conformational alteration induced by such macro-environmental conditions as temperature and pH. These latter aspects were reviewed here. Emphasized here is the importance of such immediate structural alterations that lead to an immediate activity increase, providing the immediate protection needed for the cells to survive the stress conditions.