Figure 4: Ska1 interacts with MTs by recognizing the globular regions of tubulin monomers in multiple orientations.

(a,b) Linkage map showing the sequence position of all the crosslinked residue pairs between (a) Ska1–MTBD (b) Ska complex and α1B and β2B tubulin, where 6 μM human Ska complex/Ska1–MTBD was incubated with 10 μM of MTs in the crosslinking reactions. Crosslinked products were resolved in SDS–PAGE followed by MS analysis. Red and green boxes above the β-tubulin show regions of tubulin involved in longitudinal and lateral contacts, respectively. Crosslinks observed between Ska1 R155/236/245K mutant and MTs are shown in grey. (c) Cartoon representation of tubulin dimer where residues involved in crosslinking with Ska1 residues are highlighted in stick representation. Grey and green lines denote crosslinks observed between K/R clusters of Ska1 and Glu/Asp/Tyr/Thr clusters of β-tubulin and α–tubulin, respectively. The region where Ndc80 interacts with tubulin as reported in Alushin et al.³³ is shown in yellow. Important Ska1 residues involved in MT binding are colour coded as in Figs 2 and 3.