FtsY binds to the Escherichia coli inner membrane via interactions with phosphatidylethanolamine and membrane proteins.

Targeting of many polytopic proteins to the inner membrane of prokaryotes occurs via an essential signal recognition particle-like pathway. FtsY, the Escherichia coli homolog of the eukaryotic signal recognition particle receptor alpha-subunit, binds to membranes via its amino-terminal AN domain. We demonstrate that FtsY assembles on membranes via interactions with phosphatidylethanolamine and with a trypsin-sensitive component. Both interactions are mediated by the AN domain of FtsY. In the absence of phosphatidylethanolamine, the trypsin-sensitive component is sufficient for binding and function of FtsY in the targeting of membrane proteins. We propose a two-step mechanism for the assembly of FtsY on the membrane similar to that of SecA on the E. coli inner membrane.