The endoplasmic reticulum (ER) stress response is triggered by the accumulation of unfolded proteins within the ER and is characterized by three events: the inhibition of translation (to prevent further protein accumulation), the up-regulated expression of polypeptide-folding proteins (known as the unfolded protein response or UPR) and the degradation of misfolded proteins by the ER-associated protein degradation (ERAD) system. Members of the homocysteine-inducible and ER stress-inducible ubiquitin-like domain families are components of the ERAD system and, via their ubiquitin-like domain, are thought to be involved in the destruction of misfolded proteins. HERPUD2 (Homocysteine-responsive endoplasmic reticulum-resident ubiquitin-like domain member 2) is a 406 amino acid single-pass membrane protein containing one N-terminal ubiquitin-like domain. HERPUD2 is thought to be involved in the unfolded protein response (UPR) pathway.