Gcn5p is a histone acetyltransferase (HAT) that has been shown to acetylate H3K14, H4K8 and H4K16. One of the major components of this protein is the bromodomain, which is a domain sequence found in many other proteins. The bromodomain is responsible for binding to these acetylated lysines, and allows Gcn5p to acetylate nearby residues. It should be noted that Gcn5p forms complexes with other proteins for acetylation to occur.
This model shows the key features of the Saccharomyces cerevisiae Gcn5p bromodomain and H4K16ac interactions. There is a hydrophobic binding cleft which recognises the acetylated lysine. Specificity for specific acetylated lysine residues is created by the secondary binding site which interacts with the K+2 and K+3 residues. It has been reported that Gcn5p can also bind unacetylated lysines, but this interaction is far less favourable. Nevertheless, this opens up the possibility of the bromodomain’s involvement in the lysine acetylation.
Reference: 10.1093/emboj/19.22.6141
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