The Mineralocorticoid Receptor (MR) is a ligand-activated transcription factor that mediates aldosterone signaling, regulating electrolyte balance and blood pressure in the kidney. Beyond its classical role, MR influences inflammation, fibrosis, and cardiovascular pathophysiology. As a member of the nuclear receptor superfamily, MR requires chaperone proteins for proper folding and function. Heat Shock Protein 90kDa Alpha B1 (HSP90aB1) is a molecular chaperone that stabilizes MR in its inactive state, facilitating hormone binding and nuclear translocation upon activation. Thus a functional ELISA assay was conducted to detect the interaction of recombinant human MR and recombinant human HSP90aB1. Briefly, MR was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to HSP90aB1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-MR 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 human MR and recombinant human HSP90aB1 was shown in Figure 1, the EC50?for this effect is 1.68 μg/mL.