title: Structure of mitochondrial transcription termination factor 3 reveals a novel nucleic acid-binding domain.
abstract: In mammalian cells, a family of mitochondrial transcription termination factors (MTERFs) regulates mitochondrial gene expression. MTERF family members share a approximately 270 residues long MTERF-domain required for DNA binding and transcription regulation. However, the structure of this widely conserved domain is unknown. Here, we show that the MTERF-domain of human MTERF3 forms a half-doughnut-shaped right-handed superhelix. The superhelix is built from alpha-helical tandem repeats that display a novel triangular three-helix motif. This repeat motif, which we denote the MTERF-motif, is a conserved structural element present in proteins from metazoans, plants, and protozoans. Furthermore, a narrow, strongly positively charged nucleic acid-binding path is found in the middle of the concave side of the half-doughnut. This arrangement suggests a half clamp nucleic acid-binding mode for MTERF-domains.
authors.affiliation: Dept. of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Spåhr
authors.forename: Tore
authors.initials: T
authors.lastname: Samuelsson
authors.forename: B Martin
authors.initials: BM
authors.lastname: Hällberg
authors.forename: Claes M
authors.initials: CM
authors.lastname: Gustafsson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins; D006801:Humans; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012330:RNA, Double-Stranded / Q000737:chemistry*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; C506545:MTERF2 protein, human; D024101:Mitochondrial Proteins; D012330:RNA, Double-Stranded; D014157:Transcription Factors; D004247:DNA