SRP is a complex of six distinct polypeptides and a 7S RNA that is essential for transferring nascent polypeptide chains that are destined for export from the cell to the translocation apparatus of the endoplasmic reticulum (ER) membrane [1]. SRP binds hydrophobic signal sequences as they emerge from the ribosome, and arrests translation.

1: Timeline: The strange case of the signal recognition particle. Matlin KS; Nat Rev Mol Cell Biol 2002;3:538-542. PMID:12094220