Bromodomain: Bromodomains (BRDs) are protein interaction modules that exclusively recognize acetylation motifs. BRDs are evolutionarily conserved and present in diverse nuclear proteins comprising HATs (GCN5, PCAF), ATP-dependent chromatin-remodeling complexes (BAZ1B), helicases (SMARCA), methyltransferases (MLL, ASH1L), transcriptional coactivators (TRIM/TIF1, TAFs) transcriptional mediators (TAF1), nuclear-scaffolding proteins(PB1), and the BET family. Despite large sequence variations, all BRD modules share a conserved fold that comprises a left-handed bundle of four a helices, linked by loop regions of variablelength, which line the Kac binding site and determine binding specificity. (1)

Reference
1. P. Filippakopoulos, S. Picaud, M. Mangos, T. Keates, J.P. Lambert, D. Barsyte-Lovejoy, I. Felletar, R. Volkmer, S. Müller, T. Pawson,et al.Histone recognition and large-scale structural analysis of the human bromodomain family. Cell.2012;149(1):214-231. PMID: 22464331.