title: Molecular characterization of helix-loop-helix peptides.
abstract: A class of regulators of eukaryotic gene expression contains a conserved amino acid sequence responsible for protein oligomerization and binding to DNA. This structure consists of an arginine- and lysine-rich basic region followed by a helix-loop-helix motif, which together mediate specific binding to DNA. Peptides were prepared that span this motif in the MyoD protein; in solution, they formed alpha-helical dimers and tetramers. They bound to DNA as dimers and their alpha-helical content increased on binding. Parallel and antiparallel four-helix models of the DNA-bound dimer were constructed. Peptides containing disulfide bonds were engineered to test the correctness of the two models. A disulfide that is compatible with the parallel model promotes specific interaction with DNA, whereas a disulfide compatible with the antiparallel model abolishes specific binding. Electron paramagnetic resonance (EPR) measurements of nitroxide-labeled peptides provided intersubunit distance measurements that also supported the parallel model.
authors.affiliation: Biotechnology Department, DuPont Merck Pharmaceutical Co., Wilmington, DE 19880-0328.
authors.forename: S J
authors.initials: SJ
authors.lastname: Anthony-Cahill
authors.forename: P A
authors.initials: PA
authors.lastname: Benfield
authors.forename: R
authors.initials: R
authors.lastname: Fairman
authors.forename: Z R
authors.initials: ZR
authors.lastname: Wasserman
authors.forename: S L
authors.initials: SL
authors.lastname: Brenner
authors.forename: W F
authors.initials: WF
authors.lastname: Stafford
authors.forename: C
authors.initials: C
authors.lastname: Altenbach
authors.forename: W L
authors.initials: WL
authors.lastname: Hubbell
authors.forename: W F
authors.initials: WF
authors.lastname: DeGrado
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry*; D004220:Disulfides; D004578:Electron Spin Resonance Spectroscopy; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012045:Regulatory Sequences, Nucleic Acid; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry*
chemical_list: D004268:DNA-Binding Proteins; D004220:Disulfides; D014157:Transcription Factors