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) (By similarity). Most of the substrate proteins are involved in stress regulation, lipid metabolism, intermediary metabolism, and cell wall processes (PubMed:29361248). Shows GTPase activity (PubMed:29361248, PubMed:33412199). Can also hydrolyze ATP, UTP and CTP (PubMed:33412199). The SRP-FtsY complex formation results in mutual stimulation of their GTP hydrolysis activity (PubMed:29361248). GTPase activity is stimulated by Mg(2+) or a high concentration of Mn(2+). Increasing Mg(2+) decreases the activity (PubMed:33412199). GDP acts as an inhibitor (PubMed:33412199). kcat is 0.012 sec(-1) for GTP hydrolysis (PubMed:33412199). kcat is 0.007 sec(-1) for ATP hydrolysis (PubMed:33412199). Optimum pH is 7.5-8.0. Optimum temperature is 25-37 degrees Celsius. Part of the signal recognition particle protein translocation system, which is composed of SRP and FtsY. Depletion of ffh (SRP) and ftsY results in differential expression of 14 proteins. Belongs to the GTP-binding SRP family. FtsY subfamily.