Involved in targeting and insertion of nascent membrane proteins into the cytoplasmic membrane. Binds directly to 7S RNA and mediates binding of the 54 kDa subunit of the SRP. Part of the signal recognition particle protein translocation system, which is composed of SRP and FtsY. Archaeal SRP consists of a 7S RNA molecule of 300 nucleotides and two protein subunits: SRP54 and SRP19. Belongs to the SRP19 family. Extended N-terminus.