The protein encoded by this gene is an integral membrane protein localized to the endoplasmic reticulum (ER). The encoded protein contains many tetratricopeptide repeats, sequences known for being involved in protein-protein interactions. This protein binds both the calcium uptake pump SERCA2B and the carbohydrate-binding chaperone calnexin, and it appears to play a role in calcium homeostasis in the ER. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Feb 2016].