Heat shock proteins: A review of the molecular chaperones

Two functions of heat shock proteins. Top: As new polypeptide chains (proteins) are being produced by ribosome within the cell, heat shock proteins assist in correct folding of polypeptide chain into functional protein. Presence of heat shock protein (purple) assures that the new protein will assume its functional three-dimensional configuration. Bottom: After stress event, heat shock proteins also assist in refolding or degradation of damaged or denatured proteins.

Upregulation of heat shock protein. Many types of stress are capable of increasing expression of some heat shock proteins (inducible). Stress results in activation of heat shock factor (HSF) monomers (red). HSF monomer moves from cytosol to nucleus where it combines with other monomers to form a trimer. Trimer of HSFs attaches to operator (promotor site) on heat shock gene (DNA). Attachment of trimer to operator results in production of heat shock protein messenger RNA (green), and transcription occurs in minutes. Messenger RNA moves to cytosol where heat shock protein is formed (translation).