Eukaryotic type signal recognition particle RNA

The signal recognition particle (SRP) RNA is a non-coding RNA that is part of the signal recognition particle. The signal recognition particle is a universally conserved ribonucleoprotein involved in the co-translational targeting of proteins to membranes. The eukaryotic SRP consists of a 300-nucleotide 7S RNA and six proteins: SRPs 72, 68, 54, 19, 14, and 9. Archaeal SRP consists of a 7S RNA and homologues of the eukaryotic SRP19 and SRP54 proteins. Eukaryotic and archaeal 7S RNAs have very similar secondary structures, as represented by this family. Eight helical elements fold into the Alu and S domains, separated by a long linker region [1,2]. The Alu domain is thought to mediate the peptide chain elongation retardation function of the SRP [1]. The universally conserved helix which interacts with the SRP54 M domain mediates signal sequence recognition [2,3]. In eukaryotes and archaea, the SRP19-helix 6 complex is thought to be involved in SRP assembly and stabilises helix 8 for SRP54 binding [1]. The Signal Recognition Particle Database (SRPDB) [4] provides compilations of SRP components, with phylogenetic data and structural illustrations. The human genome in particular is known to contain a large amount of SRP RNA related sequence, including Alu repeats.