TLS Online TPP Program

#Question id: 1240


Pull-down assays using proteins that ONLY bind to the GTP-bound version of the small G-protein can be used to detect when small G proteins like Rac1 have been activated by various growth factors.  You were given two lysates, one having been treated with platelet-derived growth factor (PDGF) and the other not treated with PDGF. This method is similar to performing co-IPs, so based on that knowledge, which of the following steps is erroneous?

#Unit 4. Cell Communication and Cell Signaling
  1. To assay for levels of active Rac1, PAK1-beads (the protein that only binds GTP-bound Rac1-conjugated to beads similar to Nickel beads) are added to each of the lysates described above and incubated on a rocking platform (on ice). 

  2. The tubes are vortexed well, loading buffer is added, and the samples are heated to aid in protein denaturation.

  3. The samples are loaded and analyzed by SDS-polyacrylamide gel electrophoresis, then the proteins are transferred to a membrane. 

  4. The membrane (a.k.a. blot) will be probed with the anti-Rac antibody.