3D density map of GMPCPP microtubule with fitted atomic models of tubulins seen from the minus end of the microtubule.2.5-Å-thick clipping planes move parallel to the microtubule axis from the minus end of α-tubulin to the plus end of β-tubulin and then return to the minus end of α-tubulin. α-tubulin is colored red (N domain), cyan (I domain), and magenta (C domain), whereas β-tubulin is colored brown (N domain), blue (I domain), and purple (C domain).
