ProCISE assay schematic and 20S standard curves. (A) Schematic representation of an artificial hybrid constitutive proteasome and immunoproteasome followed by chemiluminescence detection of LMP7 by the ProCISE. The chemical structure of the proteasome active site probe, PABP, is shown. (B) c20S (●) and i20S (○) standard curves (0.23-25 μg/mL) were prepared by probing with anti-20S subunit primary antibodies followed by HRP-coupled secondary antibodies and by chemiluminescence detection. The c20S standard curve is used to quantitate the β5, β1, and β2 subunits, whereas the i20S standard curve is used to quantitate the LMP7, LMP2, and MECL1 subunits. Each panel shows the relationship between luminescence intensity and c20S or i20S concentration for each individual 20S subunit.