ERβ AF-2 is required for Corepressor and Coactivator Binding. (A) Peptide competition for ERβ binding to cofactors. Binding of ERβ to GST-N-CoR was assessed in the presence of 10μg of designated competitor peptide. (B) Binding of VP16-ERβ LBD mutants to Gal-N-CoR and Gal-GRIP1 was analyzed. Luciferase activity obtained with Gal-fusion and VP16-ERβ in the presence of estradiol (100 nM) over four experiments was corrected for background and set to 100%. Activity obtained with ERβ mutants was compared to this value. Standard errors are shown.