FIG 7.

Comparison of fonticin major tube protein and related pyocin tube protein. (A) Sequence alignment of fonticin major tube protein (QQ39_04825) and pyocin tube protein (GenPept accession no. WP_003085175; PDB accession no. 3J9Q) from Pseudomonas aeruginosa (14). The sequence alignment was performed by Clustal Omega (1.2.4) software. The C-terminal part of the pyocin protein sequence (in bold) is missing in the fonticin sequence. On the right side, the tube structure is shown with a highlighted inner diameter of about 3.6 nm. (B) Side view of reconstructed pyocin tube structure. The parts highlighted in black correspond to the C terminus of the protein missing in the fonticin structure. (C) Model of pyocin tube structure with removed C-terminal 29-amino-acid residues to mimic the situation in fonticin. These residues are clearly responsible for interaction of the pyocin tube with the sheath and for stabilizing the tube stacks above each other. When the C-terminal part of the tube protein is missing, then clear necking (green arrow) of the whole tube can be seen. The images were generated using PyMOL software. (D) Averaged 2D model of fonticin tube (TEM images from Fig. 3) showing separated stacks with necking (green arrow). Similar necking can be seen in bacteriophage φ812K1-420 (52).