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. Binds to the ATPase domain of HSP/HSC70 chaperones. Binds PRKN. Detected in brain, lung, stomach, liver, kidney and testis.