Troponin I Type 2, Fast Skeletal (TNNI2) is a protein specific to fast - twitch skeletal muscles. As a component of the troponin complex, it plays a crucial role in muscle contraction regulation. TNNI2 works closely with TNNC2. When calcium ion binds to TNNC2, the conformation of TNNC2 changes and is transmitted to TNNI2, which promotes the dissociation of TNNI2 from actin and releases the inhibition, so that actin binds to myosin, triggering muscle contraction, and the interaction of the two finely regulates the process of muscle contraction.Thus a functional ELISA assay was conducted to detect the interaction of recombinant human TNNI2 and recombinant human TNNC2. Briefly, TNNI2 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to TNNC2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-TNNI2 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 μL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant humanTNNI2 and recombinant human TNNC2 was shown in Figure 1, the EC50?for this effect is 0.068ug/mL.