Fig. 6: Tertiary and quaternary structure of Pseudomonas phage Pa193 tail proteins.

a Side-view of a segment of Pa193 extended tail displayed as cartoon models. Four stacks of hexameric tube subunits (green) form the inner layer of the tail, while three layers of sheath proteins (magenta) assemble around the hexameric tube structure and comprise the outer layer of the tail. b Sheath protein (12 proteins in one complete turn) comprises a helical tail with a rise of 27.4 Å, a twist of 36.2°, and a pitch of 476.6 Å degrees. c Cartoon representation of the tail tube gp33 tertiary structure (light green) that comprises a β-sandwich (residues 9–16, 63–68, 97–114, 135–150), backbone α-helix (residues 72–85), and N-term (residues 1–8) extensions. d Cartoon representation of the sheath protein (gp32) tertiary structure including its flexible domain (residues 91–210), core (residues 23–90; 211–491), C-arm (residues 492–504), and N-arm (residues 1–22).