To establish the TR-FRET assay, N-Terminal 6×His-tagged human KEAP1 Kelch repeat domain (residues 312-624) was expressed as a tagged fusion protein in E. coli and subsequently purified via Ni-NTA resin purification, and size-exclusion chromatography. For TR-FRET, N-Terminal 6×His-tagged KEAP1 was incubated with a Europium-labeled anti-6×His antibody (LANCE-Eu-W1024 Anti 6xHis, PerkinElmer) and a Sulfo-Cy5-N3-labeled peptide probe (sequence: Ac-Propargylglycine-Peg2-LDEETGEFL-NH2) allowing the assembly of donor and acceptor dye pairs for use in protein-binding assay.