does not bind Alu. SRP9/14 is absent in the SRP of trypanosoma which instead possess a tRNA-like molecule. SRP19 SRP19 is found in the SRP of eukaryotes and Archaea. Its primary role is in preparing the SRP RNA for the binding of SRP54, SRP68, and SRP72 by properly arranging SRP RNA helices 6 and 8. Yeast SRP contains Sec65p, a larger homolog of SRP19. SRP54 Protein SRP54 (named Ffh in the bacteria) is an essential component of every SRP. It is composed of three functional domains: the N-terminal (N) domain, the GTPase (G) domain, and the methionine-rich (M) domain. SRP68 and SRP72 Proteins SRP68 and SRP72 are structurally unrelated constituents of the large domain of the eukaryotic SRP. They form a stable SRP68/72 heterodimer. About one third of the human SRP68 protein was shown to bind to the SRP RNA. A relatively small region located near the C-terminus of SRP72 binds to the 5e SRP RNA motif. References Further reading External links The SRP Database (SRPDB): Alignments of SRP RNAs and associated proteins, SRP RNA secondary structures and 3-D models Rfam entry for Metazoan type signal recognition particle RNA Rfam entry for Bacterial small signal recognition particle RNA Rfam entry for Bacterial large signal recognition particle RNA Rfam entry for Fungal signal recognition particle RNA Rfam entry for Plant signal recognition particle RNA Rfam entry for Protozoan signal recognition particle RNA Rfam entry for Archaeal signal recognition particle RNA Dnatube Signal Recognition Particle Movie RNA Protein biosynthesis Non-coding RNA