The HSP70 chaperone machinery: J proteins as drivers of functional specificity

Heat shock 70 kDa proteins (HSP70s) are ubiquitous molecular chaperones that function in modulating polypeptide folding, degradation and translocation across membranes, and protein–protein interactions. This functional diversity is driven by their interaction with J proteins — a diverse class of cofactors. Heat shock 70 kDa proteins (HSP70s) are ubiquitous molecular chaperones that function in a myriad of biological processes, modulating polypeptide folding, degradation and translocation across membranes, and protein–protein interactions. This multitude of roles is not easily reconciled with the universality of the activity of HSP70s in ATP-dependent client protein-binding and release cycles. Much of the functional diversity of the HSP70s is driven by a diverse class of cofactors: J proteins. Often, multiple J proteins function with a single HSP70. Some target HSP70 activity to clients at precise locations in cells and others bind client proteins directly, thereby delivering specific clients to HSP70 and directly determining their fate.