Figure 2. Large‐scale structural rearrangements accompany the loss of BtuB from the ColE9 translocon.

1. Superposition of the complete and partial ColE9 translocon structures (grey) aligned on OmpF. TolB in red and orange denote the full and partial translocons, respectively, ColE9 T‐domain is presented in crimson and pale orange for the full and partial translocons, respectively.
2. Side view comparison showing the relative positions of the ColE9 T‐domain (residues 85–316) in the two structures and highlighting the 15° rotation that occurs transitioning from the full (crimson) to the partial (pale orange) translocon.
3. Extracellular view of the ColE9 T‐domain position, with the OmpF trimer shown in the background. The loss of BtuB from the translocon complex elicits a 12 Å movement along the axis of rotation (black arrow) that results in repositioning of the T‐domain from a central location (crimson) to above subunit two of OmpF (pale orange).
4. TolB undergoes both rotation and translation when transitioning from the full (red) to the partial translocon (orange). The C‐terminal β‐propeller domain of TolB, which binds the ColE9 TBE, moves towards OmpF in the OM by ˜8 Å along the rotation axis.
5. View along the rotation axis from the periplasmic side of OmpF (grey surface) highlighting the 50° rotation that TolB undergoes upon loss of BtuB from the translocon complex.