Fig. 4: Structure of the functional regions in TPX2^α5-α7 bound to microtubules.

a Conformation of the functional regions and regions of interest (purple) in TPX2^α5-α7, constrained by experimental ¹³C-¹³C restraints. The γ-TuNA a and b motifs and the loop containing FKAQP motif form a helix-loop-helix structure. b Medium and long-range intramolecular ¹³C-¹H restraints in TPX2^α5-α7 on MTs, revealed by 2D CH heteronuclear correlated (HETCOR) MAS NMR spectrum. A number of intra and inter-residue contacts between amide ¹H and backbone or sidechain ¹³C atoms were identified. The inter-residue ¹³C-¹H restraints correspond to typical interatomic distances of 3–8 Å in the MAS NMR structure of TPX2^α5-α7 bound to MTs. Representative ¹³C-¹H distances in the functional motifs and loop regions are shown; the corresponding residues and atoms are shown in sticks and spheres, respectively. The spectrum was acquired on deuterated TPX2^α5-α7/MT assemblies at a magnetic field of 20.0 T and a fast MAS frequency of 60 kHz; long cross-polarization contact times of 2.7–2.8 ms were used.