title: Conserved residues make similar contacts in two repressor-operator complexes.
abstract: Comparison of a lambda repressor-operator complex and a 434 repressor-operator complex reveals that three conserved residues in the helix-turn-helix (HTH) region make similar contacts in each of the crystallographically determined structures. These conserved residues and their interactions with phosphodiester oxygens help establish a frame of reference within which other HTH residues make contacts that are critical for site-specific recognition. Such "positioning contacts" may be important conserved features within families of HTH proteins. In contrast, the structural comparisons appear to rule out any simple "recognition code" at the level of detailed side chain-base pair interactions.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors.forename: C O
authors.initials: CO
authors.lastname: Pabo
authors.forename: A K
authors.initials: AK
authors.lastname: Aggarwal
authors.forename: S R
authors.initials: SR
authors.lastname: Jordan
authors.forename: L J
authors.initials: LJ
authors.lastname: Beamer
authors.forename: U R
authors.initials: UR
authors.lastname: Obeysekare
authors.forename: S C
authors.initials: SC
authors.lastname: Harrison
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins; D005973:Glutamine; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009875:Operator Regions, Genetic; D011487:Protein Conformation; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: C063367:434-repressor protein, Bacteriophage 434; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D005973:Glutamine; D001216:Asparagine