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. Conformation of the Ffh-FtsY complex and regulation of its GTPase activity are modulated by the 4.5S RNA. Formation of the FfH-FtsY complex leads to a mutual stimulation of both GTPases. 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. Binds to SecY. Distributed between the membrane and the cytoplasm (PubMed:18281057, PubMed:8194520). Binding to the membrane probably occurs initially through phospholipid binding, which allows a strong membrane contact, followed by interaction with a membrane protein (PubMed:11353766). Targeting of FtsY to the membrane is essential for proper function (PubMed:9177162). The stability of this membrane contact may be regulated by cleavage of helix 1 (PubMed:19414018). Contains an acidic N-terminal A domain, a central N domain and a C-terminal GTPase G domain that can bind and hydrolyze GTP. Contains at least two lipid-binding sites. The first site contains the first 14 amino acids (helix 1) and the second binding site is an amphipathic alpha-helix located at the interface between the A- and the N-domain (helix 2). Proteolytically cleaved. The cleavage may regulate function and subcellular location of FtsY. Full-length FtsY is found primarily associated with the membrane, while cleaved protein is predominantly present in the cytoplasm. Deletion affects both cell morphology and protein export. Mutants are defective in the insertion into the cytoplasmic membrane of three topologically distinct membrane proteins, MalF, AcrB and FtsQ. Belongs to the GTP-binding SRP family. FtsY subfamily.