Purification of a mMED8-containing complex from rat liver. (A) Outline of purification of the mMED8-containing complex. DE52, DEAE-cellulose; P-cell, phosphocellulose. (B) TSK SW4000 gel filtration of the mMED8-containing complex. Aliquots of column fractions were analyzed by SDS/PAGE, and the mMED8 protein was visualized by immunoblotting. (C) A280 profile of the Mono Q column. (D) Cochromatography of mMED8 with components of the mMED8 ubiquitin ligase and with ubiquitin ligase activity. Aliquots of column fractions from Mono Q were analyzed by SDS/PAGE; mMED8, Cul2, and Elongin B proteins were visualized by immunoblotting.