Cyt°Chrome P450 1A1 (CYP1A1) is a member of Cyt°Chromes P450 superfamily of enzymes. Cyt°Chromes P450 are a group of heme-thiolate monooxygenases. It oxidizes a variety of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics. CYP1A1 is also known as AHH (aryl hydr°Carbon hydroxylase). It is involved in the metabolic activation of aromatic hydr°Carbons (polycyclic aromatic hydr°Carbons, PAH). Besides, Heat Sh°Ck 70kDa Protein 4 (HSPA4) has been identified as an interactor of CYP1A1, thus a binding ELISA assay was conducted to detect the interaction of recombinant rat CYP1A1 and recombinant rat HSPA4. Briefly, CYP1A1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100uL were then transferred to HSPA4-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1h with anti-CYP1A1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37°C. Finally, add 50µL stop solution to the wells and read at 450nm immediately. The binding activity of of CYP1A1 and HSPA4 was shown in Figure 1, and this effect was in a dose dependent manner.