Fig. 4.

X-ray and CryoEM structures of T4SS machine subunits and subassemblies. The schematic shows the T4SS translocation channel and conjugative pilus. Available crystal structures of homologs of individual VirB and VirD4 T4CP subunits are shown. A CryoEM structure of the pKM101-encoded core complex and an X-ray structure of the distal half (outer layer) of the core complex along with a magnified view of the pore-forming antennae projection (AP) are presented. Structures were reproduced with permission as follows: T4CP (TrwB_R388), [86]; VirB11 (Cagβ_H.p.), Yeo et al. [111]; VirB4 (TrwK_R388), Pena et al. [105]; VirB5 (TraC_pKM101), Yeo et al. [159]; VirB8 (VirB8_B.s.), [121]; Core complex CryoEM (pKM101 TraN/TraO/TraF), Fronzes et al. [33]; Core complex X-ray (pKM101, O-layer) Chandran et al. [34].