I transfected 293 cell with my protein-V5/protein-FLAG plasmid, protein-V5/FLAG-Vector, protein-FLAG/V5-vector, and used 293 not-treated as negative control, to detect whether the protein form dimer or not. I used anti-M2(FLAG) to do IP and used anti-flag or anti-v5 to do IB.
But every sample have a bond about 90KD and the size of my protein is about 90KD!!!
I have repeated times and changed to use CHO-K1 cell, but the results were similar.
It drives me crazy,,, could someone help me out?
By the way, the V5 vector is pCDNA3.1 V5-His B and the FLAG-vector is pFLAG-CMV-1, all the constructor have been sequenced.