Component of the SRP (signal recognition particle) receptor (PubMed:7844142). Ensures, in conjunction with the signal recognition particle, the correct targeting of the nascent secretory proteins to the endoplasmic reticulum membrane system (PubMed:7844142). May mediate the membrane association of SR (PubMed:7844142). Heterodimer with SRPRA. Belongs to the SRP receptor beta subunit family.