Crystal structure of a conserved N-terminal domain of histone deacetylase 4 reveals functional insights into glutamine-rich domains

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 11; pp. 4297 - 4302
• Main Authors: Guo, Liang, Han, Aidong, Bates, Darren L, Cao, Jue, Chen, Lin
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 13.03.2007; National Acad Sciences
• Subjects: Amino Acid Sequence; Amino acids; Amyloids; Biochemistry; Biological Sciences; Crystal structure; Crystallography, X-Ray - methods; Glutamine - chemistry; Histone Deacetylases - chemistry; Histones; Humans; Hydrogen bonds; Hydrogen-Ion Concentration; Models, Molecular; Molecular Sequence Data; Monomers; Mutagenesis; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins; Repressor Proteins - chemistry; Sequence Homology, Amino Acid; Social interaction; Wave diffraction; X-rays
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0608041104

Glutamine-rich sequences exist in a wide range of proteins across multiple species. A subset of glutamine-rich sequences has been shown to form amyloid fibers implicated in human diseases. The physiological functions of these sequence motifs are not well understood, partly because of the lack of structural information. Here we have determined a high-resolution structure of a glutamine-rich domain from human histone deacetylase 4 (HDAC4) by x-ray crystallography. The glutamine-rich domain of HDAC4 (19 glutamines of 68 residues) folds into a straight α-helix that assembles as a tetramer. In contrast to most coiled coil proteins, the HDAC4 tetramer lacks regularly arranged apolar residues and an extended hydrophobic core. Instead, the protein interfaces consist of multiple hydrophobic patches interspersed with polar interaction networks, wherein clusters of glutamines engage in extensive intra- and interhelical interactions. In solution, the HDAC4 tetramer undergoes rapid equilibrium with monomer and intermediate species. Structure-guided mutations that expand or disrupt hydrophobic patches drive the equilibrium toward the tetramer or monomer, respectively. We propose that a general role of glutamine-rich motifs be to mediate protein-protein interactions characteristic of a large component of polar interaction networks that may facilitate reversible assembly and disassembly of protein complexes.