From Proteopediaproteopedia link
Crystal Structure of Human Nucleosome Core Particle Containing H4K31Q mutation
[H2B1J_HUMAN] Core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling.   Has broad antibacterial activity. May contribute to the formation of the functional antimicrobial barrier of the colonic epithelium, and to the bactericidal activity of amniotic fluid.  
Publication Abstract from PubMed
Post-translational modifications (PTMs) of histones play important roles in regulating the structure and function of chromatin in eukaryotes. Although histone PTMs were considered to mainly occur at the N-terminal tails of histones, recent studies have revealed that PTMs also exist in the histone-fold domains, which are commonly shared among the core histones H2A, H2B, H3, and H4. The lysine residue is a major target for histone PTM, and the lysine to glutamine (KQ) substitution is known to mimic the acetylated states of specific histone lysine residues in vivo. Human histones H3 and H4 contain 11 lysine residues in their histone-fold domains (five for H3 and six for H4), and eight of these lysine residues are known to be targets for acetylation. In the present study, we prepared 11 mutant nucleosomes, in which each of the lysine residues of the H3 and H4 histone-fold domains was replaced by glutamine: H3 K56Q, H3 K64Q, H3 K79Q, H3 K115Q, H3 K122Q, H4 K31Q, H4 K44Q, H4 K59Q, H4 K77Q, H4 K79Q, and H4 K91Q. The crystal structures of these mutant nucleosomes were determined at 2.4-3.5 A resolutions. Some of these amino acid substitutions altered the local protein-DNA interactions and the interactions between amino acid residues within the nucleosome. Interestingly, the C-terminal region of H2A was significantly disordered in the nucleosome containing H4 K44Q. These results provide an important structural basis for understanding how histone modifications and mutations affect chromatin structure and function.
Comprehensive Structural Analysis of Mutant Nucleosomes Containing Lysine to Glutamine (KQ) Substitutions in the H3 and H4 Histone-Fold Domains.,Iwasaki W, Tachiwana H, Kawaguchi K, Shibata T, Kagawa W, Kurumizaka H Biochemistry. 2011 Sep 13;50(36):7822-32. Epub 2011 Aug 17. PMID:21812398
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.