Bromodomains represent an extensive family of evolutionarily conserved domains 
that are found in many chromatin-associated proteins such as histone 
acetyltransferases (HAT) and subunits of ATP-dependent chromatin-remodeling 
complexes. These domains are associated with acetylated lysine residues that 
bind both in vivo and in vitro; for example, they bind to the N-acetylated 
lysines of the histone tail of nucleosomes. In this report, we determined the 
structure of the bromodomain from human brahma-related gene 1 (BRG1) protein, a 
subunit of an ATP-dependent switching/sucrose nonfermenting (SWI/SNF) remodeling 
complex, and have also characterized its in vitro interaction with N-acetylated 
lysine peptides from histones. In addition to a typical all-alpha-helical fold 
that was observed in the bromodomains, we observed for the first time a small 
beta-sheet in the ZA loop region of the BRG1 protein. The BRG1 bromodomain 
exhibited binding, albeit weak, to acetylated peptides that were derived from 
histones H3 and H4. We have compared the acetyl-lysine binding sites of BRG1 
bromodomain with the yGCN5 (general control of amino acid biosynthesis). By 
modeling the acetylated-lysine peptide into the BRG1 bromodomain structure, we 
were able to explain the weak binding of acetylated-lysine peptides to this 
bromodomain.