Cryo-EM structure of the Shigella type III needle complex
Fig 7
Architecture of the export apparatus core, inner rod and start of the needle.
Cartoon representation of the subunits forming the export apparatus core, the inner rod and the start of the needle filament, in a vertical section of the outer needle complex. The individual protein components are depicted on the right side. Five SpaP, five SpaQ and one SpaR subunits, arranged in a helical fashion, form the export apparatus core. The subunits connecting the export apparatus with the needle were modeled as polyalanine peptides and adopt three different conformations (see the main text discussion about their possible identity). They share a helix-turn-helix fold and continue the export apparatus helix forming two turns. The upper turns are likely composed of needle subunits MxiH.