EBs recognize a nucleotide-dependent structural cap at growing microtubule ends.
Bottom Line: By binding close to the exchangeable GTP-binding site, the CH domain is ideally positioned to sense the microtubule's nucleotide state.The same microtubule-end region is also a stabilizing structural cap protecting the microtubule from depolymerization.This insight supports a common structural link between two important biological phenomena, microtubule dynamic instability and end tracking.
Affiliation: Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.Show MeSH
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Mentions: The only other protein known to bind to the corner of four tubulin heterodimers is doublecortin, a microtubule-stabilizing protein that is unrelated to EBs (Fourniol et al., 2010). Together, these two proteins define a polymer-specific binding mode characterized by bridging of microtubule protofilaments. Comparison of the subnanometer models of doublecortin bound to GDP microtubules and Mal3143 bound to GTPγS microtubules reveals, however, that the contacts between the corners of the four tubulin monomers and each of these proteins are not identical and, in particular, the contact with the β-tubulin H3 helix appears to be unique to EBs (Figure 6A).
Affiliation: Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.