Minor histocompatibility antigen H13

Catalyzes intramembrane proteolysis of some signal peptides after they have been cleaved from a preprotein, resulting in the release of the fragment from the ER membrane into the cytoplasm. Required to generate lymphocyte cell surface (HLA-E) epitopes derived from MHC class I signal peptides. May be necessary for the removal of the signal peptide that remains attached to the hepatitis C virus core protein after the initial proteolytic processing of the polyprotein. Involved in the intramembrane cleavage of the integral membrane protein PSEN1. Cleaves the integral membrane protein XBP1 isoform 1 in a DERL1/RNF139-dependent manner. May play a role in graft rejection (By similarity).