Involved in targeting and insertion of nascent membrane proteins into the cytoplasmic membrane. Acts as a receptor for the complex formed by the signal recognition particle (SRP) and the ribosome-nascent chain (RNC). Interaction with SRP-RNC leads to the transfer of the RNC complex to the Sec translocase for insertion into the membrane, the hydrolysis of GTP by both Ffh and FtsY, and the dissociation of the SRP-FtsY complex into the individual components. Part of the signal recognition particle protein translocation system, which is composed of SRP and FtsY. SRP is a ribonucleoprotein composed of Ffh and a 4.5S RNA molecule. In vitro purified FtsY has been shown to bind to pilE promoter DNA in a sequence-specific manner using gel retardation assay but it cannot be explained. Belongs to the GTP-binding SRP family. FtsY subfamily. Was originally thought to activate the pilin promoter.