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Crystal Structure of Dimerization Domain (1-33) of HNF-1alphaCrystal Structure of Dimerization Domain (1-33) of HNF-1alpha
Structural highlights
FunctionHNF1A_MOUSE Transcriptional activator that regulates the tissue specific expression of multiple genes, especially in pancreatic islet cells and in liver. Required for the expression of several liver specific genes. Binds to the inverted palindrome 5'-GTTAATNATTAAC-3'.[1] [2] Publication Abstract from PubMedMaturity-onset diabetes mellitus of the young (MODY) is a human genetic syndrome most commonly due to mutations in hepatocyte nuclear factor-1alpha (HNF-1alpha). Here, we describe the crystal structure of the HNF-1alpha dimerization domain at 1.7 A resolution and assess its structural plasticity. The crystal's low solvent content (23%, v/v) leads to tight packing of peptides in the lattice. Two independent dimers, similar in structure, are formed in the unit cell by a 2-fold crystallographic symmetry axis. The dimers define a novel intertwined four-helix bundle (4HB). Each protomer contains two alpha-helices separated by a sharp non-canonical turn. Dimer-related alpha-helices form anti-parallel coiled-coils, including an N-terminal "mini-zipper" complementary in structure, symmetry and surface characteristics to transcriptional coactivator dimerization cofactor of HNF-1 (DCoH). A confluence of ten leucine side-chains (five per protomer) forms a hydrophobic core. Isotope-assisted NMR studies demonstrate that a similar intertwined dimer exists in solution. Comparison of structures obtained in multiple independent crystal forms indicates that the mini-zipper is a stable structural element, whereas the C-terminal alpha-helix can adopt a broad range of orientations. Segmental alignment of the mini-zipper (mean pairwise root-mean-square difference (rmsd) in C(alpha) coordinates of 0.29 A) is associated with a 2.1 A mean C(alpha) rmsd displacement of the C-terminal coiled-coil. The greatest C-terminal structural variation (4.1 A C(alpha) rmsd displacement) is observed in the DCoH-bound peptide. Diabetes-associated mutations perturb distinct structural features of the HNF-1alpha domain. One mutation (L12H) destabilizes the domain but preserves structural specificity. Adjoining H12 side-chains in a native-like dimer are predicted to alter the functional surface of the mini-zipper involved in DCoH recognition. The other mutation (G20R), by contrast, leads to a dimeric molten globule, as indicated by its 1H-NMR features and fluorescent binding of 1-anilino-8-naphthalene sulfonate. We propose that a glycine-specific turn configuration enables specific interactions between the mini-zipper and the C-terminal coiled-coil. The dimerization domain of HNF-1alpha: structure and plasticity of an intertwined four-helix bundle with application to diabetes mellitus.,Narayana N, Hua Q, Weiss MA J Mol Biol. 2001 Jul 13;310(3):635-58. PMID:11439029[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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