Signal recognition particle

This article is missing information about overall structure (as context for "S domain" pics and for mechanism description); rough structure and function of binding proteins. Please expand the article to include this information. Further details may exist on the talk page. (October 2021)

The signal recognition particle (SRP) is an abundant, cytosolic, universally conserved

The function of SRP was discovered by the study of processed and unprocessed secretory proteins, particularly immunoglobulin light chains;^[2] and bovine preprolactin. Newly synthesized proteins in eukaryotes carry N-terminal hydrophobic signal sequences, which are bound by SRP when they emerge from the ribosome.^[3][4]

Mechanism

In

In eukaryotes there are three domains between SRP and its receptor that function in guanosine triphosphate (GTP) binding and hydrolysis. These are located in two related subunits in the SRP receptor (SRα and SRβ)^[7] and the SRP protein SRP54 (known as Ffh in bacteria).^[8] The coordinated binding of GTP by SRP and the SRP receptor has been shown to be a prerequisite for the successful targeting of SRP to the SRP receptor.^[9][10]

Upon docking, the nascent peptide chain is inserted into the translocon channel where it enters into the ER. Protein synthesis resumes as SRP is released from the ribosome.^[11][12] The SRP-SRP receptor complex dissociates via GTP hydrolysis and the cycle of SRP-mediated protein translocation continues.^[13]

Once inside the ER, the signal sequence is cleaved from the core protein by signal peptidase. Signal sequences are therefore not a part of mature proteins.

Composition and evolution

Despite SRP function being analogous in all organisms, its composition varies greatly. The SRP54-

Autoantibodies and disease

• Signal recognition particle RNA

References