Dimeric structures of the PCAF HAT domain. A) The PCAF dimer structure mediated by a four helical bundle; B) The PCAF dimer structure mediated by β-sheet extension; C) Close-up view of detailed interactions within the PCAF dimeric interface shown in A; D) Close-up view of detailed interactions in the PCAF dimeric interface shown in B. The structures are presented in ribbon with each monomer colored in cyan, magenta, green and blue. Helices, β-strands and loops are labeled with α, β and L, respectively. The cofactor acetyl-CoA is represented in sticks (A and B). Amino acids that are involved in direct contacts are represented as sticks and also labeled (C and D). Hydrogen bonds are indicated with yellow broken lines.