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Figure 5
Possible modes for the cooperative binding of doublecortin to microtubules and for microtubule bundling. Schematic microtubules are shown as grey spheres polymerized from α-tubulin and β-tubulin (shades of grey). The exposure of β-subunits at the (+)-end and of α-subunits at the (–)-end of the microtubule determines its polarity. N-DCX (red spheres) binds to the vertex of four αβ-tubulin dimers. Only every other N-DCX binding site around the circumference of the microtubule is occupied in this scheme. Distances between these N-DCX molecules are given, along with the dimension of the staggered C-DCX tetramer (left) and the maximum dimension of the linker region between N-DCX and C-DCX (centre). The linker between N-DCX and C-CDCX is drawn as a black line (not to scale). The microtubule is less densely decorated with doublecortin in vivo (estimated at a physiological doublecortin:αβ-tubulin ratio of ∼1:70; Taylor et al., 2000 ![]() |