[The pleiotropic activity of heat-shock proteins]

Abstract

Stress or heat-shock proteins (HSPs) are highly conserved proteins present in cells of both prokaryotes and eukaryotes, providing them with protection from cellular and environmental stress factors.Based on molecular-weight, HSPs can be divided into the large (HSP100: 100-110 kDa and HSP90: 75-96 kDa), intermediate (HSP70: 66-78 kDa, HSP60, and HSP40), and small (sHSP:8.5-40 kDa) subfamilies. These proteins play an essential role as molecular chaperones/co-chaperones by assisting the correct folding of nascent and stress-accumulated protein-substrate assembly,preventing the aggregation of these proteins, as well as transport across membranes and the degradation of other proteins. Members of HSP family display dual activity depending on the irintra- or extracellular distribution. Intracellular HSPs mainly play a protective role. Extracellular or membrane-bound HSPs mediate immunological functions. Among the functions of HSPs is their participation in cell signaling. This review deals with the structure and properties of the main members of the HSPs and their role in a large number of cellular/extracellular processes.