The information on requirements for T4SS substrate-channel dockingCertain T4SS substrates require secretion chaperones for translocation.
These chaperones often possess physical properties (small size of 15 kDa, acidic pI, and amphipathic helices)
resembling those of chaperones associated with the type III secretion systems, a family of macromolecular translocation systems ancestrally related to bacterial flagella.
| # | Accessory protein(GI) | motif(s) | Substrate(s) | Function | Reference |
| 1 | VirC1 (16119796) | ND | VirD2 | VirC1 pairwise interacts with the processing factors VirD2 relaxase, VirC2, and VirD1 to stimulate generation of multiple copies per cell of the T-DNA substrate. VirC1 promotes conjugative T-DNA transfer. | (1) PubMed: 17505518 |
| 2 | VirE1 chaperone (16119804) | CT50aa sufficient (interacts with the VirD4 T4CP. CT100aa(VirE2) sufficient for the T4CP interation) | VirE2 | Translocation of the VirE2 effector through the A. tumefaciens VirB/VirD4 T4SS requires VirE1. | (2) PubMed: 19946141 |
Tips:1.Substrate(s): For the conjugation systems,
the listed proteins are relaxases that bind a cognate T4CP and are delivered to recipient cells.
For the effector translocator systems, the listed proteins are effectors that play a role in the infection processes of the bacterial pathogen.
2.motif(s):The motifs listed are required for substrate translocation.
In some cases, the protein or its C-terminal fragment (CT) is sufficient to mediate translocation to target cells,
as shown by fusion to a reporter protein such as Cre recombinase or adenylate cyclase.
Amino acids (aa) at positions listed relative to the C-terminal fragment (subscript) are required for translocation,
as shown by mutational analysis.
ND, not determined. Parentheses indicate that the interaction between a protein substrate
and a cognate T4CP has been experimentally shown.
3.Accessory protein: Accessory factors required for T4SS channel docking or translocation.
The proposed function in mediating substrate-T4SS channel docking is shown in parentheses.
PubMed:19946141
(1) Atmakuri K; Cascales E; Burton OT; Banta LM; Christie PJ (2007). Agrobacterium ParA/MinD-like VirC1 spatially coordinates early conjugative DNA transfer reactions. EMBO J. 26(10):2540-51. [PudMed:17505518] 
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(2) Alvarez-Martinez CE; Christie PJ (2009). Biological diversity of prokaryotic type IV secretion systems. Microbiol Mol Biol Rev. 73(4):775-808. [PudMed:19946141]
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T4SS ID
Information of structure: 
VirB8
Genes in the 5-Kb flanking regions if available, or non-essential genes in the T4SS gene cluster if any.
