title: Creating temperature-sensitive winged helix transcription factors. Amino acids that stabilize the DNA binding domain of HNF3.
abstract: Winged helix transcription factors contain two polypeptide loops, or "wings," that make minor groove contacts with DNA from either side of a three-helix bundle that binds the DNA major groove. While wing 1 is stabilized by a beta-sheet, parameters that stabilize wing 2 are unknown. Herein we identify two bulky aromatic residues in wing 2 that stabilize the loop structure and, thereby, the entire protein's DNA binding and transcriptional stimulatory activity by interacting with other residues in the three-helix bundle. Mutations of these wing 2 residues create proteins that are temperature-sensitive for transcriptional activity. Aromatic and/or hydrophobic residues are highly conserved among the 150 known winged helix proteins, suggesting conserved function. We suggest that the winged helix structure evolved by the acquisition of aromatic and/or hydrophobic residues in distal polypeptide sequences that helped stabilize the association of a protein loop (wing 2) with the three-helix bundle, thereby enhancing DNA binding.
authors.affiliation: Cell and Developmental Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: K
authors.initials: K
authors.lastname: Stevens
authors.forename: L
authors.initials: L
authors.lastname: Cirillo
authors.forename: K S
authors.initials: KS
authors.lastname: Zaret
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D018257:Helix-Loop-Helix Motifs; D051541:Hepatocyte Nuclear Factor 3-alpha; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D051541:Hepatocyte Nuclear Factor 3-alpha; D009687:Nuclear Proteins; D014157:Transcription Factors