title: Crystal structure of the P2 C-repressor: a binder of non-palindromic direct DNA repeats.
abstract: As opposed to the vast majority of prokaryotic repressors, the immunity repressor of temperate Escherichia coli phage P2 (C) recognizes non-palindromic direct repeats of DNA rather than inverted repeats. We have determined the crystal structure of P2 C at 1.8 Å. This constitutes the first structure solved from the family of C proteins from P2-like bacteriophages. The structure reveals that the P2 C protein forms a symmetric dimer oriented to bind the major groove of two consecutive turns of the DNA. Surprisingly, P2 C has great similarities to binders of palindromic sequences. Nevertheless, the two identical DNA-binding helixes of the symmetric P2 C dimer have to bind different DNA sequences. Helix 3 is identified as the DNA-recognition motif in P2 C by alanine scanning and the importance for the individual residues in DNA recognition is defined. A truncation mutant shows that the disordered C-terminus is dispensable for repressor function. The short distance between the DNA-binding helices together with a possible interaction between two P2 C dimers are proposed to be responsible for extensive bending of the DNA. The structure provides insight into the mechanisms behind the mutants of P2 C causing dimer disruption, temperature sensitivity and insensitivity to the P4 antirepressor.
authors.affiliation: Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Tariq
authors.initials: T
authors.lastname: Massad
authors.forename: Karin
authors.initials: K
authors.lastname: Skaar
authors.forename: Hanna
authors.initials: H
authors.lastname: Nilsson
authors.forename: Peter
authors.initials: P
authors.lastname: Damberg
authors.forename: Petri
authors.initials: P
authors.lastname: Henriksson-Peltola
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Haggård-Ljungquist
authors.forename: Martin
authors.initials: M
authors.lastname: Högbom
authors.forename: Pål
authors.initials: P
authors.lastname: Stenmark
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D017901:Bacteriophage P2 / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D003461:Crystallography; D004247:DNA / Q000737:chemistry*; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009875:Operator Regions, Genetic; D011485:Protein Binding; D012091:Repetitive Sequences, Nucleic Acid; D017384:Sequence Deletion; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C117790:C protein, Enterobacteria phage P2; D014764:Viral Proteins; D004247:DNA; D000409:Alanine