Extended Data Figure 7: Sequence alignments of the gp9 L-loop-like peptides in phage tail proteins.

a, Sequence alignment of the gp9 L-loop and L-loop-like peptides from short non-contractile tails. Conserved residues are boxed and coloured red. The core hydrophobic region of the L loop is indicated by a dashed box. b, Sequence alignment of gp9 L loop, HIV fusion peptide, influenza fusion peptide and a potential hydrophobic membrane active peptide of the bacteriophage T4 tail protein gp5. Conserved residues are boxed and coloured red. Completely conserved residues are shown in white on a red background. The core region of the HIV fusion peptide is indicated by a dashed box. c, Schematic diagram showing a possible mechanism for the exposure of the potential T4 hydrophobic membrane active peptide during infection. The structure of the T4 gp27 (top β-barrels) and gp5 (bottom) complex is shown in ribbon representation. The potential hydrophobic peptide of gp5 is coloured red. The rest of the complex structure is coloured grey. The potential hydrophobic peptide is exposed after the release of the gp5 C-terminal needle. Conformational changes of the lysozyme domain trigger the insertion of the hydrophobic peptide into the membrane.