FIG 4.

Structure of the flagellar collar in ΔmotB B. burgdorferi. (A to D) 3D surface view of the whole collar complex in ΔmotB B. burgdorferi. The collar is ∼79 nm in diameter and embeds on the IM. Each known collar protein has 16 copies and assembles into a ring structure. The membrane of the spirochetal cells shows a clear curvature and distorts the collar complex (C and D). The height of the collar is 20 nm on the flat IM (C) and 23 nm on the curved IM (D). The inner diameter of the FlcC ring is 36 nm on the flat IM (C) and 39 nm on the curved IM (D). The FlcA proteins are colored in ice, FlcB in green, FlcC in light blue, and FlbB in purple. The unknown collar proteins are colored in dark blue.