Studies of acetylation and deacetylation in high mobility group proteins. Identification of the sites of acetylation in high mobility group proteins 14 and 17.

Duck erythrocytes were incubated with [3H]acetate both in the presence and absence of sodium butyrate. Subsequent perchloric acid extraction of the nuclei, followed by selective acetone precipitation, CM-Sephadex ion exchange chromatography, and gel filtration yielded radioactively labeled high mobility group (HMG) proteins HMG-14 and HMG-17 in pure form. Extensive enzymatic degradation of the proteins followed by amino acid analysis of the digests yielded a significant amount of material eluting in the position of epsilon-N-acetyllysine. Furthermore, automated Edman degradation of intact 3H-labeled HMG-14 and HMG-17 identified the specific sites of acetylation of these proteins. In both erythrocyte HMGs isolated from cells not exposed to butyrate, the lysine residue at position 2 was the only one found to be labeled. However, one additional site in HMG-14 and two additional sites in HMG-17 were found in the proteins from cells incubated in butyrate. Finally, studies of the enzymatic deacetylation of HMG-14 and HMG-17 confirmed that both nuclear proteins serve as deacetylase substrates and that butyrate inhibits their deacetylation, just as in the case of other HMG proteins and nucleosomal core histones.