FIG 3.
Identification of stator B subunit location and binding sites. (A) Two-dimensional (2D) slice of subtomogram-averaged structure of the top part of the Vibrio motor in the KK148 strain. The components of the H ring have been labeled as FlgO, FlgP, and FlgT. The black arrow shows an additional/uncharacterized density beneath the T ring. OM, outer membrane. (B) A 2D slice view of the averaged structure of the top part of the Vibrio motor in KK148 ΔpomAB. The region indicated by the arrow shows the loss of density beneath the T ring, suggesting that the cryo-ET density beneath the T ring is derived from the PomB protein. (C) The atomic structure of PomBC5 was fitted into the 13 cryo-ET densities (purple) beneath the T ring. (D) Zoomed-in view shows a stator B unit within the dimer directly interacting via a PG-binding site with 2 units of MotX located at the bottom of the T ring. (E, F) Superimposition of the cryo-ET density map (mesh) and the atomic models of FlgT, MotY, MotX, and PomB. The models are shown as ribbon diagrams and colored as in panel D.