Introduction of alanines at Rem positions R200, L227, and H229 disrupts the interaction with β_1a. (A) In the duplicate representative experiments shown, a monoclonal antibody directed to Rem was used to immunoprecipitate V-Rem–YFP-β_1a complexes from tsA201 cells expressing YFP-β_1a (lanes 2 and 6), YFP-β_1a and V-Rem (lanes 3 and 7), and YFP-β_1a and V-Rem AAA (lanes 4 and 8). Blots were probed with an antibody directed to XFP (see Materials and methods). (B) Similar affinity of the Rem antibody for V-Rem and V-Rem AAA is presented, where the immunoprecipitated Rem and Rem AAA are detected by the Rem antibody (lanes 3–4 and 7–8). (C) Comparable expression of YFP-β_1a, V-Rem, and V-Rem AAA in harvested tsA201 cells is confirmed in total lysates before coimmunoprecipitation. Lanes 1 and 5 are loaded with protein markers (molecular weights indicated). Results shown are representative of five separate experiments.