Intradimer curvature of “straight” and “bent” tubulin heterodimers.

For the RB3-SLD-bound structures, the orientations of the longitudinally-paired α1β1 and α2β2 heterodimers with respect to the MT plus (+) and minus (−) ends are shown in Figure S4 of Text S1 along with the relative orientations of the D1-(α1β1) and D1-(α2β2) dimers in the GTP-tubulin-D1 DARPin structures. Crystal structures are listed in order of decreasing resolution. Residues comprising the α- and β-H7 helices used for angle calculations are listed in Table S3 of Text S1. Each angle was measured using the backbone N-Cα-C-O, Cα, and all atoms, with the standard deviation shown accordingly.*Control calculations of the “straight” tubulin were performed on the epothilone A- and docetaxel-bound, Zn2+-stabilized protofilament tubulin with respect to the taxol-bound, Zn2+-stabilized protofilament tubulin (α-H7: 224–242, β-H7: 224–243).**Outlying values of intradimer tubulin curvature T2R-vinblastine structure are likely due to unraveling of the H7 helix.