May function as a nucleotide exchange factor for HSP/HSP70, promoting ADP release, and activating Hsp70-mediated refolding. Inhibits both auto-ubiquitination of PRKN and ubiquitination of target proteins by PRKN (By similarity). Binds to the ATPase domain of HSP/HSC70 chaperones. Binds PRKN (By similarity). The fifth BAG domain is responsible for the interaction with HSP70 nucleotide-binding domain.