Biochemical analysis of epitope-tagged IRK3 channels. Immunoprecipitation of radiolabeled tagged IRK3 channel proteins with P5D4 (A) and AU1 (B) antibodies. A specific 57-kDa band was immunoprecipitated in VSV, VSV(Y2F), and AU1-IRK3-MDCK cells (A, lanes 2 and 3, and B, lane 2, respectively) but not in the absence of P5D4 and AU1 antibodies (A, lanes 4 and 5, and B, lane 3, respectively) nor in MDCK cells (A, lane 1, and B, lane 1). (C) VSV-IRK3 protein (lane 1) was not sensitive to PNGaseF and endo H treatment (lanes 2 and 3, respectively). Numbers on the left indicate mobility of prestained molecular mass standards in kDa.