Component of the signal recognition particle (SRP) complex, a ribonucleoprotein complex that mediates the cotranslational targeting of secretory and membrane proteins to the endoplasmic reticulum (ER) (By similarity). SRP9 together with SRP14 and the Alu portion of the SRP RNA, constitutes the elongation arrest domain of SRP (By similarity). The complex of SRP9 and SRP14 is required for SRP RNA binding (By similarity). Heterodimer with SRP14; binds RNA as heterodimer (By similarity). Component of a signal recognition particle complex that consists of a 7SL RNA molecule and six protein subunits: srp72, srp68, srp54, srp19, srp14 and srp9 (By similarity). Belongs to the SRP9 family.