BCL2-associated athanogene 2 （BAG2） belongs to the Bag family of proteins. BAG2 is a chief component of the HSC 70/CHIP chaperone-dependent ubiquitin ligase complex and acts to upset CHIP-mediated ubiquitylation. BAG proteins compete with Hip for attaching to the Hsc70/Hsp70 ATPase domain and promote substrate discharge. All the BAG proteins have a roughly 45 amino acid BAG domain by the C-terminus but vary clearly in their N-terminal regions. The BAG domains of BAG1， BAG2， and BAG3 act together expressly with the Hsc70 ATPase domain in vitro and in mammalian cells. All three proteins attach with high affinity to the ATPase domain of Hsc70 and obstruct its chaperone activity in a Hip-repressible manner.
