Proposed mechanism for the recognition of GTP microtubules by kinesin and EB1. (A) GTP form of β-tubulin seen from the plus end. Binding site (KB) for loop L11 (blue) of kinesin (white ribbon) is elevated toward kinesin. (B) GDP form of β-tubulin seen from the plus end. Binding site for kinesin is down and away from kinesin (see Video 3 for details). (C) Side view of KB formed between helix H4 of β-tubulin and helix H11’ of α-tubulin. (D) View from the outside of the microtubule. KB is located near an OC as the putative binding site for EB1 (EB). The conserved acetylation site of Lys-40 of α-tubulin (star) is accessible from outside of the microtubule. Bars, 2 nm.