Protein Kinase R (PKR) is activated by double-stranded RNA (dsRNA), the synthesis of which is caused virally. PKR can also be activated by the protein PACT or by heparin. It plays a key role in the innate immune response to viral infection and is also involved in the regulation of signal transduction, apoptosis, cell proliferation and differentiation. Besides, Cyclin Dependent Kinase 1 (CDK1) has been identified as an interactor of PKR, thus a binding ELISA assay was conducted to detect the interaction of recombinant human PKR and recombinant human CDK1. Briefly, PKR were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100uL were then transferred to CDK1-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1h with anti-PKR 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 PKR and CDK1 was shown in Figure 1, and this effect was in a dose dependent manner.