Figure 9.

Hexagonal disc formed by six IglA/IglB heterodimers of F. novicida T6SS shown as viewed from the top (A), from the side (B), and stacked as a sheath of 11 discs (C). For comparison, the contracted pyocin sheath (pdb 3J9R) is also shown (D). Each heterodimer is shown as a ribbon diagram. In (C), the IglA/B heterodimers of the bottom disc are colored as in (B) and the heterodimers that are connected by IglB β-strand connectors are given the same color. In (D), pyocin sheath subunits connected by C-terminal β-strand connectors are given the same color. In both (C) and (D) the sheath subunits connected by β-strand connectors form 6-start right handed helices. (A,B) Adapted from Clemens et al. (2015) with permission.