title: Structural analysis of a novel class of R-M controller proteins: C.Csp231I fromCitrobactersp. RFL231.
abstract: Controller proteins play a key role in the temporal regulation of gene expression in bacterial restriction-modification (R-M) systems and are important mediators of horizontal gene transfer. They form the basis of a highly cooperative, concentration-dependent genetic switch involved in both activation and repression of R-M genes. Here we present biophysical, biochemical, and high-resolution structural analysis of a novel class of controller proteins, exemplified by C.Csp231I. In contrast to all previously solved C-protein structures, each protein subunit has two extra helices at the C-terminus, which play a large part in maintaining the dimer interface. The DNA binding site of the protein is also novel, having largely AAAA tracts between the palindromic recognition half-sites, suggesting tight bending of the DNA. The protein structure shows an unusual positively charged surface that could form the basis for wrapping the DNA completely around the C-protein dimer.
authors: Biophysics Laboratories, Institute of Biomedical and Biomolecular Sciences, School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK. john.mcgeehan@port.ac.uk
authors: J E
authors: JE
authors: McGeehan
authors: S D
authors: SD
authors: Streeter
authors: S-J
authors: SJ
authors: Thresh
authors: James E N
authors: JEN
authors: Taylor
authors: M B
authors: MB
authors: Shevtsov
authors: G G
authors: GG
authors: Kneale
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002954:Citrobacter / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D055503:Protein Multimerization; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial