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 o ccurs via an essential signal recognition particle-like pathway. FtsY, the Escherichia coli homolog of the eukaryotic signal recognition particle rece ptor alpha -subunit, binds to membranes via its amino-terminal AN domain. W e demonstrate that FtsY assembles on membranes via interactions with phosph atidylethanolamine and with a trypsin-sensitive component. Both interaction s are mediated by the AN domain of FtsY, In the absence of phosphatidyletha nolamine, the trypsin-sensitive component is sufficient for binding and fun ction 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.