Figure 2: Global Conformational Change within γ-TuRC.

a. Cartoon for calculating the radius of γ-TuRC at each spoke from its γ-tubulin (red) to the axis of the γ-tubulin helix (black dashed line).

b. Radius of γ-TuRC measured for Class 1 (blue) and Class 2 (pink) at each of the 14 spokes. The radius was measured from the center of each γ-tubulin subunit (approximated by the Cα of Tyr-169) to the central axis of the γ-tubulin helix. As a point of comparison, the radius of tubulin in the 13 protofilament MT, taken as half the average between the outer diameter of 250 Å and inner diameter of 170 Å, is shown as a dashed line at 105 Å.

c. All Cα displacement vectors for γ-tubulin residues between Class 1 and Class 2. Class 1 of γ-TuRC is shown as a gray cartoon, where non-γ-tubulin components are partially transparent. Displacement vectors required to move each γ-tubulin Cα to its position in Class 2 are shown as red lines.

d. Schematic for measuring orthogonal displacement vectors of each γ-tubulin subunit between Class 1 and Class 2. The overall displacement vector of the Tyr-169 centroid of each γ-tubulin between the two conformations was decomposed into three orthogonal components: left/right, along the vector between γ-tubulin residues Ile-318 to Arg-124, down-up, along the vector between Arg-244 to Asn-102, and in-out, along the vector between Ser-226 to Asp-159.

e. Measurement of the displacements of the 14 γ-tubulins of γ-TuRC from Class 1 to Class 2, calculated using the strategy in panel (C). Three components of motion are plotted: left (negative) to right (positive), as a solid line; down (negative) to up (positive), as a dotted line, and in (negative) to out (positive), as a dashed line.