A Refined Model of the Prototypical Salmonella SPI-1 T3SS Basal Body Reveals the Molecular Basis for Its Assembly
Figure 5
Molecular basis for the SPI-1 basal body assembly.
(A) Overlaid view of the interface formed by the RBMs of adjacent molecules for InvG (orange) and PrgH (green for domain 1, blue for domain 2) in the ring models. In all three cases, the orientation of the domains is similar, with the two helices stacking against the three-stranded sheet. (B) Electrostatic surface representation of individual subunits from the PrgHperiplasmic (bottom) and InvG (top) ring models. The charged surfaces forming the basis of the interaction between RBMs are indicated in grey boxes. (C) Electrostatic surface representation of the InvG ring model (top) and PrgH periplasmic domain ring model (bottom). The negative charge at the bottom of the InvG ring, as well as the positive charge on the top of the PrgH ring, is shown, suggesting a charge-driven mechanism for the assembly of the Salmonella SPI-1 T3SS basal body. The positively charged interior of the InvG N0 ring is also visible.