RAC1 and RAC2 interact with distinct sets of proteins.

<p>K562 cells were transduced with retroviral constructs containing Avi-tagged RAC1 (Avi-RAC1) or RAC2 (Avi-RAC2) and BirA biotin ligase, or BirA-only control construct (BirA) sorted, and streptavidin-based pull-down assay was performed. Bound fractions were then used for mass spectrometry analysis to identify RAC1- or RAC2-specific interaction partners (experimental setup shown in A). (B) Efficiency of the pull-down assay was assessed by Western blot detecting Avi-tagged RAC1 and RAC2. T: total cell lysate fraction; B: bound fraction; NB: non-bound fraction. (C) Mass spectrometry analysis identified 335 RAC1-specific and 229-RAC2-specific peptides using 90% protein/90% peptide confidence cut-off. (D) Cytospins of GFP-RAC1- or GFP-RAC2-transduced TF-1 cells were analyzed for RAC localization. Syto62 was used to stain the nucleus.