Fig. 4: TPX2 N-terminus enhances condensation and MT nucleation efficiency.

a Schematic of full-length TPX2 and various N-terminal and C-terminal truncation constructs used. b Epifluorescent images of GFP-TPX2 (green) and Cy5-labeled tubulin (magenta) co-condensates at 1 µM and 10 µM (equimolar concentration) for indicated TPX2 truncation construct. Representative of three experimental replicates. c Quantification of relative tubulin signal in co-condensate (partition coefficient) as a function of TPX2 concentration. Mean values (points) with ± 1 SD as error bars from a representative experiment are plotted and a line was fit; n of condensates per condition are: NT_1-319—406, 572, 278, 217, 292, 276, and 268 for 250, 500 nM, 1, 2.5, 5, 10, and 25 μM [TPX2/TB], respectively; NT_1-480—254, 49, 256, 286, 283, 273, 271, and 198 for 100, 250, 500 nM, 1, 2.5, 5, 10, and 25 μM [TPX2/TB], respectively; CT_319-716—275, 323, 296, and 297 for 2.5, 5, 10, and 25 μM [TPX2/TB], respectively; CT_480-716—327 and 253 for 10 and 25 μM [TPX2/TB], respectively. See also Supplementary Fig. 5a–d for partition coefficient measures of GFP-TPX2 signal. d Rate of MT nucleation as a function of TPX2 concentration for indicated constructs. Full-length data previously shown (Fig. 3c). Rates for each concentration of a given construct are normalized to the maximum rate of that construct (absolute maximum rates between all constructs are within a twofold range). Lines of best fit shown. See also Supplementary Fig. 5e, f for individual rate curves and Supplementary Movie 6. e Different efficiencies of MT nucleation for the full-length and CT_480-716 TPX2 construct. Efficiency values are the inverse of the TPX2 concentration at which half the maximum rate of MT nucleation is achieved ([TPX2]⁻¹ at Rate_1/2Max); efficiency values were normalized to full length (efficiency of 1). The difference (fold change) in efficiencies is shown (∆). Source data are provided as a Source Data file.