Signal recognition particle, SRP54 subunit (IPR022941)

Short name: SRP54

Family relationships


This entry represents the SRP54 subunit of the signal recognition particle protein translocation system.

The signal recognition particle (SRP) is a multimeric protein, which along with its conjugate receptor (SR), is involved in targeting secretory proteins to the rough endoplasmic reticulum (RER) membrane in eukaryotes, or to the plasma membrane in prokaryotes [PMID: 17622352, PMID: 16469117]. SRP recognises the signal sequence of the nascent polypeptide on the ribosome. In eukaryotes this retards its elongation until SRP docks the ribosome-polypeptide complex to the RER membrane via the SR receptor [PMID: 12605305]. Eukaryotic SRP consists of six polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72) and a single 300 nucleotide 7S RNA molecule. The RNA component catalyses the interaction of SRP with its SR receptor [PMID: 17507650]. In higher eukaryotes, the SRP complex consists of the Alu domain and the S domain linked by the SRP RNA. The Alu domain consists of a heterodimer of SRP9 and SRP14 bound to the 5' and 3' terminal sequences of SRP RNA. This domain is necessary for retarding the elongation of the nascent polypeptide chain, which gives SRP time to dock the ribosome-polypeptide complex to the RER membrane. In archaea, the SRP complex contains 7S RNA like its eukaryotic counterpart, yet only includes two of the six protein subunits found in the eukarytic complex: SRP19 and SRP54 [PMID: 12364595].

The bacterial homologues of the SRP54 protein and SRP RNA are Ffh and 4.5S RNA. They comprise a minimal bacterial SRP that can target ribosome-nascent chain complexes to the plasma membrane via interaction with FtsY, the bacterial homologue of the SRP receptor [PMID: 9799502, PMID: 10656787].

GO terms

Biological Process

GO:0006614 SRP-dependent cotranslational protein targeting to membrane

Molecular Function

GO:0005525 GTP binding
GO:0003924 GTPase activity

Cellular Component

GO:0048500 signal recognition particle

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.