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. Author manuscript; available in PMC: 2014 Oct 2.
Published in final edited form as: Curr Opin Struct Biol. 2014 Apr 5;0:16–23. doi: 10.1016/j.sbi.2014.02.006

Figure 1.

Figure 1

Schematic of the T4S system. Subunits at the right, identified with the A. tumefaciens VirB/VirD4 nomenclature, assemble as the T4S apparatus/ pilus across the Gram-negative cell envelope. Hexameric ATPases establish contacts with the integral inner membrane (IM) subunits to form an inner membrane complex. VirB7, VirB9, and VirB10 form a core complex extending from the IM, periplasm, and outer membrane (OM). A domain of unspecified composition (grey bullet structure) and the pilus assemble within the central chamber of the core complex.