Surface representations of side and top views of the Ndc80/Nuf2 dimer–microtubule complex. The side views are oriented such that the plus end of the microtubule is at the top of the page. All views were colored using a cylinder radius that depicts the tubulin density as green and the Ndc80/Nuf2 dimer density as blue (Pettersen et al., 2004). Side and top views in A–C are contoured such that only the strongest, well-ordered density regions are visualized. Side and top views in D–F are contoured to show both strong and weak densities. Two sequential asymmetrical densities are clearly visible in the longitudinal slices, B and E, from the respective contoured views of the three-dimensional map, A and D. Top views of the slices are shown in C and F. Bars, 25 nm.