Fig. 2.

Three-dimensional maps of the hook. (a) A section taken perpendicular to the helical axis. (b) A cylindrical section through the wall of the central tube. The rod-like features lining the central putative protein channel are spaced about 1 nm apart in the azimuthal (horizontal) direction. (c) A vector diagram showing the directions that the 5, 11, 6, and 1 start helices in b. (d) A surface representation of the hook density map. (e) A surface representation with the front half of the structure removed to reveal domain D0. The three domains of the hook subunit are labeled D0, D1, and D2. (Scale bar: 10 nm.)