title: DNA binding of Escherichia coli arginine repressor mutants altered in oligomeric state.
abstract: The Escherichia coli arginine repressor (ArgR) controls expression of the arginine biosynthetic genes and acts as an accessory protein in Xer site-specific recombination at cer and related plasmid recombination sites. The hexameric wild-type protein shows L-arginine-dependent DNA binding. In this work, ArgR mutants that are defective in trimer-trimer interactions and bind DNA as trimers in an L-arginine-independent manner are isolated and characterized. Whereas the wild-type ArgR hexamer exhibits high-affinity binding to two repeated ARG boxes separated by 3 bp (each ARG box containing two identical dyad symmetrical 9 bp half-sites), the trimeric mutants bind to and footprint three adjacent half-sites of this 'idealized' substrate. Trimeric ArgR is impaired in its ability to repress the arginine biosynthetic genes and in Xer site-specific recombination. In the absence of L-arginine, residual wild-type ArgR-binding occurs as trimers. The binding of an N-terminal 77-amino-acid DNA-binding domain to idealized ARG boxes is also characterized.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: S H
authors.initials: SH
authors.lastname: Chen
authors.forename: A F
authors.initials: AF
authors.lastname: Merican
authors.forename: D J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D001120:Arginine / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008970:Molecular Weight; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C087018:ArgR protein, Bacteria; C490177:ArgR protein, E coli; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D001120:Arginine