Why does NRF2 migrate at a larger size than the theoretical MW?

The larger NRF2 size is likely due to a secondary structure or modification, which is not uncommon. Under normal conditions, KEAP1 targets NRF2 for degradation through the polyubiquitination/proteasome pathway, which makes it hard to detect the protein in cells (some cell lines have mutations in the NRF2 pathway that may cause NRF2 accumulation). After certain treatments, KEAP1 is modified and cannot bind NRF2, so NRF2 is not polyubiquitinated and will accumulate and enter the nucleus to activate transcription of its targets. Because polyubiquitination may result in different numbers of ubiquitin molecules binding to the same target protein, most polyubiquitinated proteins will not appear as distinct bands on western blot, but as a smear or ladder in some cases.

Last updated: December 8, 2023