Fig. 1.

Identification of proteins proximal to PS in live cells. a Schematic illustration of biotinylation of proteins proximal to PS with GFP-BirA*-2xPH. b COS-1 cells stably expressing GFP-BirA*-2xPH were incubated with or without 50 µM biotin for 24 h. The cells were then fixed, permeabilized, and stained for TfnR and biotin with Alexa594-streptavidin. c, d Lysates from cells in b were mixed with streptavidin-coupled magnetic beads. The proteins pulled down by the beads were blotted with streptavidin-HRP in c, or the indicated antibodies in d. Nuclei were stained with DAPI. Scale bars, 10 μm