Complex of Rbx1 (Ring-Box 1), Cul4B (cullin 4B), Dcaf11 (Ddb1- and Cul4-associated factor 11) and Ddb1 (Damage specific DNA binding protein 1. Recombinant Rbx1, encompassing amino acids 2-108(end), mutated at M5I, contains an N-terminal His-tag (6xHis). Recombinant Cul4B, encompassing amino acids 3-913(end), contains an N-terminal His-tag (6xHis). Recombinant Dcaf11, encompassing amino acids 2-546(end), contains an N-terminal FLAG-tag. Recombinant human Ddb1, encompassing amino acids 2-1140(end) contains an N-terminal FLAG-tag. These recombinant proteins were co-expressed, and affinity purified.