Figure 6. Analysis of Truncated, Artificially Dimerized Dynein Motors in the Optical Trapping Assay and Illustration of the “Compact” and “Extended” Dynein Conformations.

(A) Compact and extended conformations of the dynein dimer may explain a wide variation in step size. In its compact state, the two dynein rings are restrained and located in close proximity and perhaps overlapping due to direct head-to-head “interactions” or a “zipping” of the proximal tail. The loss of physical interactions or an “unzipping” of the proximal tail might cause a less restrained extended conformation with an increased head-to-head distance.

(B) Diagram of constructs showing the dynein heavy chain truncations and tags.

(C) Force production and stepping behavior of GST-Dyn1_331kDa. Left: Schematic of the GST-Dyn1_331kDa motor. Center: Histograms of the combined step size data (gray-shaded), classified according to the advancing (red histogram bars) and nonadvancing modes (blue histogram bars) (3 pN force-feedback data, n = 670). Right: Stall force distribution of GST-Dyn1_331kDa (4.8 pN ± 1.0 pN; mean ± SD; n = 195).

(D) Force production and stepping behavior of GST-Dyn1_314kDa. Left: Schematic of the GST-Dyn1_314kDa motor. Center: Histograms of the combined, advancing and non-advancing step size data (3 pN force-feedback data, n = 518). Right: Stall force distribution of GST-Dyn1_314kDa (4.0 pN ± 1.1 pN; mean ± SD; n = 91).

(E) Force production and stepping behavior of the dynein construct GST-α2-Dyn1_314kDa with artificial linker elements. Left: Schematic of the GST-α2-Dyn1_314kDa motor. Center: Histograms of the combined, advancing, and nonadvancing step size data (3 pN force-feedback data, n = 457). Right: Stall force distribution of GST-α2-Dyn1_314kDa (5.2 pN ± 1.1 pN; mean ± SD; n = 80).