Scintillation proximity assay for total p53 protein as an alternative to ELISA

Measurement of the level of a specific protein can be an important parameter to discern as that can change and reflect disease status. A number of methods have been developed to quantitate the level of a protein, some amenable to high throughput screening. A method is described to measure the total level of the tumor suppressor p53 using scintillation proximity assay (SPA) beads and radiolabeled streptavidin. Three different cell extracts were used, with one used to develop the standard curve for the amount of p53. This method allows the specific detection of p53 in the range of 50 to 300 pg in 10 µl of an extract. While this detection is less than what can be detected by commercially available enzyme linked immunosorbent assay (ELISA) kits, the SPA compares favorably on time required and cost. This new assay also has the potential to be coupled with measurements for p53 DNA binding, a unique aspect of this approach.