Structure analysis of the membrane-bound PhoD signal peptide of the Tat translocase shows an N-terminal amphiphilic helix

► Structural characterization of the Tat signal peptide of PhoD in membranes ► The N-terminal domain is an amphiphilic helix that can bind to the membrane surface. ► The hydrophobic domain contains two adjacent helical segments. ► Membrane binding of the signal peptide may precede Tat translocation.