title: Three-dimensional structure of the bifunctional protein PCD/DCoH, a cytoplasmic enzyme interacting with transcription factor HNF1.
abstract: The bifunctional protein pterin-4a-carbinolamine dehydratase (PCD)/dimerization cofactor of HNF1 (DCoH) is a cytoplasmic enzyme involved in the tetrahydrobiopterin regeneration and is found in complex with the transcription factor HNF1 in liver cell nuclei. An atypical hyperphenylalaninemia and the depigmentation disorder vitiligo are related to a deficiency of PCD/DCoH activity. The crystal structure of PCD/DCoH was solved by multiple isomorphous replacement and refined to a crystallographic R-factor of 20.5% at 2.7 A resolution. The single domain monomer comprises three alpha-helices packed against one side of a four-stranded, antiparallel beta-sheet. The functional enzyme is a homo-tetramer of 222 symmetry where each of the monomers contributes one helix to a central four helix bundle. In the tetramer two monomers form an eight-stranded, antiparallel beta-sheet with six helices packing against it from one side. The concave, hydrophobic surface of the eight-stranded beta-sheet with its two protruding loops at either end is reminiscent of the saddle-like shape seen in the TATA-box binding protein. PCD/DCoH binds as a dimer to the helical dimerization domain of dimeric HNF1 forming a hetero-tetramer possibly through a mixed four helix bundle.
authors.affiliation: EMBL, Structural Biology Programme, Heidelberg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Ficner
authors.forename: U H
authors.initials: UH
authors.lastname: Sauer
authors.forename: G
authors.initials: G
authors.lastname: Stier
authors.forename: D
authors.initials: D
authors.lastname: Suck
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D006836:Hydro-Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009687:Nuclear Proteins; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D006836:Hydro-Lyases; C076392:pterin-4a-carbinolamine dehydratase