The Creb binding domain assumes a structure comprising of three alpha-helices which pack in a bundle, exposing a hydrophobic groove between alpha-1 and alpha-3 within which complimentary domains found in the protein 'activator for thyroid hormone and retinoid receptors' (ACTR) can dock. Docking of these domains is required for the recruitment of RNA polymerase II and the basal transcription machinery [1].

1: Mutual synergistic folding in recruitment of CBP/p300 by p160 nuclear receptor coactivators. Demarest SJ, Martinez-Yamout M, Chung J, Chen H, Xu W, Dyson HJ, Evans RM, Wright PE; Nature. 2002;415:549-553. PMID:11823864