Regulated changes in protein conformation can have profound effects on protein function, although routine laboratory methods often fail to detect them. The recently discovered BAG-family proteins may operate as bridging molecules that recruit molecular chaperones to target proteins, presumably modulating protein functions through alterations in their conformations, and ultimately affecting diverse cellular behaviours including cell division, migration, differentiation and death. Emerging knowledge about BAG-family proteins indicates that there may be a mechanism for influencing signal transduction through non-covalent post-translational modifications.