title: Amino acid-amino acid contacts at the cooperativity interface of the bacteriophage lambda and P22 repressors.
abstract: The bacteriophage lambda repressor and its relatives bind cooperatively to adjacent as well as artificially separated operator sites. This cooperativity is mediated by a protein-protein interaction between the DNA-bound dimers. Here we use a genetic approach to identify two pairs of amino acids that interact at the dimer-dimer interface. One of these pairs is nonconserved in the aligned sequences of the lambda and P22 repressors; we show that a lambda repressor variant bearing the P22 residues at these two positions interacts specifically with the P22 repressor. The other pair consists of a conserved ion pair; we reverse the charges at these two positions and demonstrate that, whereas the individual substitutions abolish the interaction of the DNA-bound dimers, these changes in combination restore the interaction of both lambdacI and P22c2 dimers.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: F W
authors.initials: FW
authors.lastname: Whipple
authors.forename: E F
authors.initials: EF
authors.lastname: Hou
authors.forename: A
authors.initials: A
authors.lastname: Hochschild
mesh_terms: D000595:Amino Acid Sequence; D017100:Bacteriophage P22 / Q000235:genetics / Q000378:metabolism*; D010582:Bacteriophage lambda / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D016384:Consensus Sequence; D017124:Conserved Sequence; D019281:Dimerization; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins