Translocon-associated protein subunit alpha is a protein that in humans is encoded by the SSR1 gene. The signal sequence receptor (SSR) is a glycosylated endoplasmic reticulum (ER) membrane receptor associated with protein translocation across the ER membrane. The SSR consists of 2 subunits, a 34-kD glycoprotein encoded by this gene and a 22-kD glycoprotein. This gene generates several mRNA species as a result of complex alternative polyadenylation. This gene is unusual in that it utilizes arrays of polyA signal sequences that are mostly non-canonical. [provided by RefSeq].
TRAP proteins are part of a complex whose function is to bind calcium to the ER membrane and thereby regulate the retention of ER resident proteins. May be involved in the recycling of the translocation apparatus after completion of the translocation process or may function as a membrane-bound chaperone facilitating folding of translocated proteins.