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 (PubMed:34388369). Enhances the enzymatic activity of SPC and facilitates the interactions between different components of the translocation site (By similarity). Component of the signal peptidase complex paralog A (SPC-A) composed of a catalytic subunit SEC11A and three accessory subunits SPCS1, SPCS2 and SPCS3 (PubMed:34388369). Component of the signal peptidase complex paralog C (SPC-C) composed of a catalytic subunit SEC11C and three accessory subunits SPCS1, SPCS2 and SPCS3 (PubMed:34388369). Within the complex, interacts with SEC11A or SEC11C and SPCS1 (PubMed:34388369). 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 (PubMed:34388369). This ensures the selectivity of the complex towards h-regions shorter than 18-20 amino acids (PubMed:34388369). Belongs to the SPCS2 family.