Uncovering functional residues of all 10 TPX2 repeats. (A) Schematic overview of critical residues in all 10 repeats of TPX2 based on mutational analyses, where substitution with alanine significantly reduces MT-binding affinity. (B) Images showing the binding of indicated GFP-LZ–tagged TPX2 single repeats or corresponding mutants on dynamic MTs grown in assay buffer containing no KCl. w/o KCl, without KCl. (C) Images showing the binding of indicated GFP-LZ–tagged TPX2 combined repeats or corresponding mutants harboring a mutation in indicated single repeats on dynamic MTs grown in assay buffer containing no KCl. (D) Images showing the binding of indicated GFP-LZ–tagged TPX2 combined repeats or corresponding mutants harboring a simultaneous mutation of all component repeats on dynamic MTs grown in assay buffer containing no KCl. (E) Quantification of the ratio of indicated mutant fluorescence intensity versus corresponding WT fluorescence intensity on GMPCPP seeds and GDP-MT lattices for experiments shown in B–D. n = 11–14 MTs from two experiments. Scale bars, 2 μm. Data represent mean ± SD.