title: Structure and dynamics of the tetrameric mnt repressor and a model for its DNA complex.
abstract: Abstract   The tetrameric Mnt repressor of bacteriophage P22 consists of two dimeric DNA-binding domains and a tetramerization domain. The NOE and chemical shift data demonstrate that the structures of the domains in the wild-type repressor protein are similar to those of the separate domains, the three-dimensional structures of which have been determined previously. (15)N relaxation measurements show that the linker that connects the anti-parallel four-helix bundle with the two β-sheet DNA-binding dimers is highly flexible. No evidence was found for interactions between the distinct modules. The (15)N relaxation properties of the two domains differ substantially, confirming their structural independence. A model in which one two-stranded coiled coil of the four-helix bundle is attached to one N-terminal dimer is most consistent with the biochemical data and (15)N relaxation data. For the Mnt-DNA complex this geometry fits with a model in which the two β-sheet DNA-binding domains are bound at two successive major grooves of the Mnt operator and the tetramerization domain is packed between these two DNA-bound dimers. In such a model the two-fold symmetry axis of the four-helix bundle coincides with that of the operator sequence and the two bound dimers. Bending of the Mnt operator of approximately 30° upon binding of the tetramer, as measured by gel-shift assays, is in agreement with this model of the Mnt-DNA complex.
authors.affiliation: a      Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research   ,  Utrecht University   ,  Padualaan 8 ,    3584   ,    CH Utrecht   ,    The Netherlands.
authors.forename: I M
authors.initials: IM
authors.lastname: Nooren
authors.forename: G E
authors.initials: GE
authors.lastname: Folkers
authors.forename: R
authors.initials: R
authors.lastname: Kaptein
authors.forename: R T
authors.initials: RT
authors.lastname: Sauer
authors.forename: R
authors.initials: R
authors.lastname: Boelens
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D004247:DNA