Fig. 4: Sheath initiator accommodates the symmetry mismatch from the sheath (C6 symmetry) to the baseplate (C3 symmetry).
From: Atomic structures of a bacteriocin targeting Gram-positive bacteria
a Interactions between the sheath initiator and the baseplate shown in perpendicular views. Two conformers of the sheath initiator (shown as pink and blue surfaces) bind to the hub-hydrolase alternatively. b Ribbon diagrams of the two conformers of the sheath initiator. The structures are rainbow colored from N-terminus (blue) to C-terminus (red). Differences between the two conformers are present at the N-terminal loops; C-terminal globular domains are the same. c Two interfaces on the C-terminal domain of the sheath initiator (gray surface) with the sheath and the triplex core bundle. d Close-up view of the handshake β-sheet formed by the C-terminal domain of the sheath initiator and two neighboring sheath subunits. e Close-up view of the interface between the C-terminal domain of the sheath initiator and the triplex core bundle. f Close-up view of the interfaces between sheath initiators and the hub-hydrolase. The N-terminal loops of adjacent sheath initiators adopt different conformations to bind at the junction of hub domains.
