Figure 2.

A T3S effector trapped inside the secretion tunnel. The T3SS needle complex atomic structure of Salmonella enterica was determined in two functional states. Here with the secretion substrate trapped inside (PDB id 7ahi) [21]. (a) A calculated 5 Å map of the atomic model is shown for simplicity. Substrate is displayed in magenta, T3SS needle complex in light purple. (b) Zoom on the needle and the secretion tunnel. (c,d) Smoothed surface of the tunnel displayed in light blue. The tunnel has a right-handed helical grooved surface and is wide enough to allow secretion substrates to form α-helices. In (c) the molecular surface representation of the substrate is shown. In (d) the cartoon representation is shown.