Component of the signal peptidase complex (SPC) which catalyzes the cleavage of N-terminal signal sequences from nascent proteins as they are translocated into the lumen of the endoplasmic reticulum. Enhances the enzymatic activity of SPC and facilitates the interactions between different components of the translocation site. Component of the signal peptidase complex (SPC) composed of a catalytic subunit sec11 and three accessory subunits spc1, spc2 and spc3 (By similarity). The complex induces a local thinning of the ER membrane which is used to measure the length of the signal peptide (SP) h-region of protein substrates. This ensures the selectivity of the complex towards h-regions shorter than 18-20 amino acids (By similarity). SPC associates with the translocon complex (By similarity). Belongs to the SPCS2 family.