Solution structures of the N-terminal domain of histone H-4

Histones, nuclear proteins that interact with DNA to form nucleosomes, are essential for both the regulation of transcription and the packaging of DNA within chromosomes. The N-terminal domain of histone H4 contains four acet ylation sites at lysine residues and may play a separate role in chromatin structure from the remainder of the H4 chain. We performed circular dichroi sm and NMR characterization of both native (H4(NTP)) and acetylated (Ace-H4 (NTP)) peptides containing N-terminal acetylation domain of histone H4 for various pH environments. Data from CD and NMR suggested that H4 NTP exhibit ed a pH-dependent conformational change, whereas the Ace-H4(NTP) is insensi tive to pH change. However, both peptides showed a defined structural form at acidic pH environments. The solution structure for Ace-H4(NTP) shows two structurally independent regions comprising residues of Leu(10)-Gly(13) an d Arg(19)-Leu(22), demonstrating relatively well-defined turn-type structur es. Our results suggest that N-terminal acetylated region of H4 prefers an extended backbone conformation at neutral pH, however, upon acetylation, th e regions containing lysine residues induce structural transition, having d efined structural form for its optimum function.