Total protein of psoriasis patients’ skin samples (n=4) was collected and dilution to 1 ml. 1 μg Recombinant Human GPCR MRGX2 protein (GST tag) was added into the protein solution, rotate for 4 h at room temperature. Then the anti-GST magnetic bead was used for get the binding protein of MRGPRX2. Polypeptide segments were detected by liquid chromatography-mass spectrometry.