Towards a Structural Comprehension of Bacterial Type VI Secretion Systems: Characterization of the TssJ-TssM Complex of an Escherichia coli Pathovar
Figure 5
Schematic representation of the enteroaggregative E. coli T6SS.
The outer (OM) and inner membranes (IM) are represented in light green. The T4 phage-like central puncturing device includes Hcp (green disks) and VgrG (purple). The “tail sheath” TssBC (VipAB) proteins are shown in blue, around the central Hcp/VgrG pilum. The TssBC proteins constituting a sheath encompassing the Hcp tube has not been evidenced but is speculated based on the similarities between the T6SS TssBC subunits and the bacteriophage T4 sheath [4], [17]. The three-transmembrane inner membrane TssM protein (yellow) interacts with the TssL IM protein (blue) [20]. TssL interacts with TagL (green), an IM protein that anchors the T6SS to the cell wall [22]. TssM C-terminal domain interacts with a loop of the outer membrane lipoprotein TssJ [this study]. In this model, the TssL-TagL-TssM-TssJ complex forms a trans-envelope spanning channel.