VirB9/CagX/TrbG, a component of the type IV secretion system.
VirB9 is a component of the type IV secretion system, which is employed by pathogenic bacteria to export virulence proteins directly from the bacterial cytoplasm into the host cell. Unlike the more common type III secretion system, type IV systems evolved from the conjugative apparatus, which is used to transfer DNA between cells. VirB9 was initially identified as an essential virulence gene on the Agrobacterium tumefaciens Ti plasmid. In the pilin-like conjugative structure, VirB9 appears to form a stabilizing complex in the outer membrane, by interacting with the lipoprotein VirB7. The heterodimer has been shown to stabilize other components of the type IV system. This alignment model spans the C-terminal domain of VirB9. CagX is a component of the Helicobacter pylori cag PAI-encoded type IV secretion system. Some other members of this family are involved in conjugal transfer to T-DNA of plant cells.
Structure:2OFQ: NMR structure of a complex between the C-terminal domain of VirB9 and a VirB7 interaction domain as exemplified by the homologs TraO and TraN from plasmid pKM101, contacts at 4 A
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