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 play a role in graft rejection. 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 (PubMed:11714810, PubMed:12077416, PubMed:12145199, PubMed:14741365). Cleaves the integral membrane protein XBP1 isoform 1 in a DERL1/RNF139- dependent manner (PubMed:25239945).
3423-; H13; hIMP1; histocompatibility (minor) 13; histocompatibility 13; HM13; IMP-1; IMP1; IMPAS-1; Intramembrane protease 1; minor histocompatibility antigen 13; Minor histocompatibility antigen H13; Presenilin-like protein 3; PSL3; Signal peptide peptidase; signal peptide peptidase beta; signal peptide peptidase like 1