Structure of MTs, zinc-sheets and zinc-macrotubes.

(A) The protofilament arrangements are modified from Wolf et al. (1993). Arrows represent the polarity of a protofilament, and color discriminates the outer side (green) from the inner side (blue) of a MT. Dashed lines indicate the cut plane of the cross-cut views in B. (B) The cross-cut views of a MT (left), zinc-sheet and zinc-macrotube (right). Red stars denote a helix 12 that is closely related to dynein and kinesin binding sites. (C) General views, close-up views and diffraction patterns of MTs (left), zinc-sheets (middle) and zinc-macrotubes (right). (D and E) The width and length distribution of zinc-sheets measured in EM images. The mean ± SD and number of counted zinc-sheets (N) are shown.