The Dam1 complex recruits the Ndc80 complex to dynamic microtubule plus ends. (A) Microtubule-binding activity of Ndc80 was tested in the absence and presence of equimolar amounts of Dam1 complex and 100 mM NaCl. (B, top) TIRF micrographs showing little microtubule (MT) decoration of the Ndc80 complex under physiological ionic strength. (bottom) The Dam1 complex efficiently recruits Ndc80 to taxol-stabilized microtubules. SN, supernatant; P, pellet. Bar, 4 µm. (C) Still image and kymograph of a time-lapse video demonstrate that in the presence of 100 nM unlabeled Dam1 complex, Ndc80–EGFP tracks microtubule plus ends (Video 7). Arrowhead indicates Ndc80–EGPF at the tip of the microtubule. (D) Streaming video showing continuous tip tracking of Ndc80–EGFP in the presence of unlabeled Dam1 (Video 8). (E) The Dam1–Alexa Fluor 594 complex and Ndc80–EGFP colocalize at microtubule plus ends during microtubule polymerization and depolymerization (Video 9). (F) Intensity scan demonstrating that Dam1 signals on the microtubule lattice correlate with the signal intensity profile of the Ndc80 complex. Bars, 2 µm.