Skip to main content
. 2015 Sep 14;6:8179. doi: 10.1038/ncomms9179

Figure 2. Structure and flexibility of superposed dimers.

Figure 2

(a,b) Averaged images of superposed dimers from sparse regions. (a) Classified to reveal the rings and stalks connecting the motor to the track. Stalk flexibility alters the distance between the rings and MT surface. (b) Classified to reveal the GST (arrows) variably positioned between the ring and the MT surface. Number of images in each class varies between 10 and 23. (c–e) Averaged images of dimers from crowded regions. (c) Well-populated classes show the stalk and stalkheads clearly despite stalk flexibility. (d) Combined images including those from (c) shows flexibility occurs mainly in the plane of the image (double-headed arrow). Hinge between stalk and stalkhead (white arrow) and binding site at the interface of tubulin subunits (bracket) are indicated. (e) Class averages of aligned head domains showing the ring substructure. Prominent peripheral features (asterisks in middle panel) are compatible with features (asterisks) seen in computed projections (g) of a model (h) of the ADP-dynein superposed dimer bound to the MT (chimera of dynein motor from PDB 3VKG and stalkhead from PDB 3J1T; see Methods and Supplementary Figs 5–7). (f) Diagram depicting four MT protofilaments, staggered axially by 0.9 nm, each comprising dimers of α- (grey) and β- (white) tubulin subunits at 8.3-nm intervals. Stalkhead binding sites (black triangles) deduced for the superposed dynein configuration on adjacent protofilaments are illustrated. (h) Surface rendered model of the superposed dimer. Motor structure coloured as in Fig. 1a. AAA+ domains (1–6) are indicated. The GST dimer is depicted connecting to the linkers by magenta springs. (i) Enlargement of boxed (stalkhead) region of (h) showing one stalk depicted as backbone ribbons and showing location of invariant prolines P3371 and P3496 (red spacefill) and the position of the flexible hinge (black ring). (j) Model in (h) viewed looking towards the MT minus end; the front-to-back arrangement of the two motors shows how the linker (L) and C-terminal domain (C) of the two motors face one another (red arrow). Scale bars in (a) for (a–c,e), and in (d) for (d,f–h and j) are 8 nm.