Molecular characterization of Escherichia coli FtsE and FtsX

The genes ftsE and ftsX are organized in one operon together with ftsY. Fts Y codes for the receptor of the signal recognition particle (SRP) that func tions in targeting a subset of inner membrane proteins. We have found no in dications for a structural relationship between FtsE/X and FtsY. Evidence i s presented that FtsE and FtsX form a complex in the inner membrane that be ars the characteristics of an ATP-binding cassette (ABC)-type transporter. FtsE is a hydrophilic nucleotide-binding protein that has a tendency to dim erize and associates with the inner membrane through an interaction with th e integral membrane protein FtsX. An FtsE null mutant showed filamentous gr owth and appeared viable on high salt medium only, indicating a role for Ft sE in cell division and/or salt transport.