Heat Shock 70kDa Protein 5 (HSPA5)

Binding immunoglobulin protein (BiP) is a molecular chaperone that uses ATP/ADP cycling to regulate protein folding by the protein disulfide isomerase (PDI) family of proteins. It is a 78kDa glucose-regulated heat shock protein and is involved in unfolded protein response. HSPA5 is its human gene. It binds to immunoglobulin heavy chain.

When the nucleotide-binding domain of GRP78 interacts with ATP, its substrate-binding domain can interact with unfolded/misfolded protein. Subsequent ATP hydrolysis acts to strengthen the interaction between GRP78 and the unfolded/misfolded protein. Under these conditions PDI can then work to promote disulfide oxidation and rearrangement until the correct protein conformation is achieved.