title: Domains of Mnt repressor: roles in tetramer formation, protein stability, and operator DNA binding.
abstract: The Mnt repressor of bacteriophage P22 is a member of the ribbon-helix-helix family of gene regulatory proteins. Proteolytic cleavage of Mnt with chymotrypsin reveals that it consists of two structural domains. Both domains are required for high-affinity operator binding. The N domain (residues 1-51) is dimeric and binds weakly but specifically to operator DNA. The C domain (residues 52-82) forms an independent alpha-helical, tetramerization domain and, by itself, has no DNA-binding activity. In intact Mnt, the N and C domains help to stabilize each other against denaturation but appear to be linked rather flexibly. Assays of the half-operator affinities of Mnt and the isolated N domain indicate that binding to adjacent half-sites in the whole operator is stabilized by protein-protein contacts between N domains in addition to protein-protein contacts between C domains.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Waldburger
authors.forename: R T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D017100:Bacteriophage P22 / Q000235:genetics*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins