Fig. 7. Cell stimulation increases the association of NDP kinase and Rac with cell membranes. (A) Merged image of serum-starved cells treated with EGF for 2 minutes and stained for Rac (red) and NDP kinase (Ab-1; green); areas of overlap appear in yellow. The line scan analysis shows the fluorescence intensities of Rac and NDP kinase along the white line in the image. Scale bar, 25 µm. (B) Subcellular fractionation of quiescent and serum-treated cells was as in Methods. The particulate fraction was immunoblotted with antibodies to NDP kinase (NDPK), Rac and Na⁺,K⁺-ATPase, a plasma membrane marker.