The N-CoR β-box binds ERβ. (A) Peptide competitions. Binding of ERβ to either bacterially expressed GST-N-CoR (amino acids 2239–2453) was determined in the presence of increasing doses of competitor peptide (amounts shown at top refer to μg of peptide, plus signs refer to the presence of estradiol in the assay). (B) Interaction of ERβ with different peptides in mammalian two-hybrid assays. A representative experiment is shown. Errors are derived from three separate wells. (C) Analysis of ERβ interaction with mutant Gal-N-CoR fusion proteins. Values were determined as in Fig. 3.