The pod components of the

The bacterial type III secretion system (T3SS) uses a membrane-embedded injectisome assembly to export effector proteins into host cells. While atomic-level structural details have been revealed for much of the T3SS apparatus, the model of the cytoplasmic sorting platform remains largely low-resolution. A central structural element of the sorting platform is the so-called "pod" protein, SctQ, which anchors the sorting platform to the inner membrane via interaction with the adaptor protein SctK, and connects to the central ATPase via the spoke protein SctL. SctQ proteins also interact with alternatively translated homodimers of their C-terminal SPOA2 domains. Low resolution electron density maps have provided an outline of the sorting platform architecture, and fluorescence microscopy studies have suggested a 1:4:2 SctK:SctQ:SctL stoichiometry. While there are experimental and AlphaFold structures of the individual components or complexes of sorting platform pod, there is currently no model for the pod structure that adequately fits the electron density or accounts for the proposed stoichiometry. Here we use AlphaFold to generate a model of the