Structure-based design of pyrimidine core molecules based on the ER/SRC-2 interaction (3erd). A, Rendering of SRC-2 peptide from 3erd crystal structure (the internal H691 and R692 residues are deleted for clarity); B, Minimized structure of CBI 2,4-diisobutylamino-6-isopentylpyrimidine; C, Overlay of the SRC-2 peptide and CBI; D, Side-view of SRC-2 peptide and CBI overlay in coactivator groove.