Figure 1: Schematic of type IV secretion components and their interactions.Fronzes et al. (2009) Nat Rev Micro, 7, 703-714.
Figure 2: The number of VirB/D genes. Numbers in inside circle represent VirB/D genes downloaded from NCBI and UniprotKB, whereas other in outside circles are the num of predicted VirB/D genes(Putative and Homolog of VirB/D genes) by our bioinformatical tools.
GeneType Function Verified genes* Putative Genes$ Homolog of VirB/D#
VirB1 Punch holes in the cell wall 22 163 1749
VirB2 Pilus subunit 44 603 5636
VirB3 Pass membrane protein 56 411 2521
VirB4 Energizes substrate transport 92 733 6053
VirB5 Pilus subunit 40 263 3173
VirB6 Translocation channel at the inner membrane 96 856 4046
VirB7 Component of a complex to span the cell envelope 16 67 3822
VirB8 Translocation channel at the inner membrane 100 655 3447
VirB9 Component of a complex to span the cell envelope 67 673 2937
VirB10 Component of a complex to span the cell envelope 56 645 1668
VirB11 Energizes substrate transport 73 582 12914
VirD4 Energizes substrate transport 55 540 3101
Sum   717 6191 51067
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*: “Experimentally verified VirB/D genes (EVG)” are genes mentioned in published research articles with well clarified as one component of T4SS in database, and with clearly functional description.
$:Putative genes are VirB/D genes predicted based on genomic location and homology. Besides owning similarly sequences, these putative VirB/D genes are located nearby with each other in a genome island of chromosome. These genes have higher possibility to be functional T4SS Genes.
#:Homolog VirB/D Genes were predicted by T4SP program in bacterial genomes. They usually own similar protein sequences or functional domain with proven VirB/D genes. However their function needs to be further proven.