The actin assembly-promoting activity of GxcM relies on interaction with Fbp17. (A–H) Localization of the indicated fluorescent proteins in randomly migrating cells. (A) WT cells expressing GFP-Fbp17 and RFP. (B) WT cell expressing GFP-Fbp17 and GxcM-RFP. (C) WT cells expressing GFP-Fbp17 and GxcM^4A-RFP. (D) WT cell expressing GFP-Fbp17 and GxcM^N790-RFP. (E) WT cell expressing GFP-Fbp17^ΔSH3 and GxcM-RFP. (F) WT cells expressing GFP-Fbp17^SH3 and GxcM-RFP. (G)fbp17^– cells expressing GxcM-GFP and LimEΔcoil-RFP. (H)fbp17^– cells expressing GxcM-RFP and GFP-ArpC4. (I and J) Time-lapse imaging of fbp17⁻ cells migrating under agarose along a folic acid gradient. (I)fbp17⁻ cells expressing GxcM-GFP and LimEΔcoil-RFP. (J)fbp17⁻ cells expressing GxcM-RFP and GFP-ArpC4. Angle-series plots on the right show fluorescent intensity distribution of the indicated proteins along the perimeter of the cell, with 0° and +180°/−180° corresponding to the migrating front and rear, respectively. Solid lines represent the mean and shades represent mean ± SD. n, number of cells analyzed. Scale bars, 5 μm.