Thermally driven rotational Brownian motion and gliding of a microtubule bound to a single kinesin molecule in presence of 5 μM ATP. (A) Left, single frame of rhodamine-labeled microtubule exhibiting random rotations and motion along its major axis. Right, scheme of analysis. The fit gives an angle (θ), measured from an arbitrary x axis to the major axis, the center (asterisk), and the length of the ellipse. Cross, pivoting point. Scale bar, 2 μm. (B) Six original angular traces of freely rotating and gliding microtubules tethered by full-length kinesin-1 molecules. (C) Six original angular traces of microtubules, using ΔT kinesin construct. (D) Six original angular traces, using ΔTΔH kinesin.