title: Hyperthermophilic Thermotoga arginine repressor binding to full-length cognate and heterologous arginine operators and to half-site targets.
abstract: The degree of sequence conservation of arginine repressor proteins (ArgR) and of the cognate operators (tandem pairs of 18 bp imperfect palindromes, ARG boxes) in evolutionarily distant bacteria is unusually high, and the global mechanism of ArgR-mediated regulation appears to be similar. However, here we demonstrate that the arginine repressor from the hyperthermophilic bacterium Thermotoga neapolitana (ArgR(Tn)) exhibits characteristics that clearly distinguish this regulator from the well-studied homologues from Escherichia coli, Bacillus subtilis and B.stearothermophilus. A high-resolution contact map of ArgR(Tn) binding to the operator of the biosynthetic argGHCJBD operon of Thermotoga maritima indicates that ArgR(Tn) establishes all of its strong contacts with a single ARG box-like sequence of the operator only. Protein array and electrophoretic mobility-shift data demonstrate that ArgR(Tn) has a remarkable capacity to bind to arginine operators from Gram-negative and Gram-positive bacteria, and to single ARG box-bearing targets. Moreover, the overall effect of L-arginine on the apparent K(d) of ArgR(Tn) binding to various cognate and heterologous operator fragments was minor with respect to that observed with diverse bacterial arginine repressors. We demonstrate that this unusual behaviour for an ArgR protein can, to a large extent, be ascribed to the presence of a serine residue at position 107 of ArgR(Tn), instead of the highly conserved glutamine that is involved in arginine binding in the E.coli repressor. Consistent with these results, ArR(Tn) was found to behave as a superrepressor in E.coli, inhibiting growth in minimal medium, even supplemented with arginine, whereas similar constructs bearing the S107Q mutant allele did not inhibit growth. We assume that ArgR(Tn), owing to its broad target specificity and its ability to bind single ARG box sequences, might play a more general regulatory role in Thermotoga
authors.affiliation: Laboratoire de Biotechnologie, FRE CNRS 2230 Unité Biocatalyse, Faculté des Sciences et Techniques, Université de Nantes, 2 rue de la Houssinière, 44322, Nantes, France.
authors.forename: Amélie
authors.initials: A
authors.lastname: Morin
authors.forename: Nadine
authors.initials: N
authors.lastname: Huysveld
authors.forename: Frédérique
authors.initials: F
authors.lastname: Braun
authors.forename: Diliana
authors.initials: D
authors.lastname: Dimova
authors.forename: Vehary
authors.initials: V
authors.lastname: Sakanyan
authors.forename: Daniel
authors.initials: D
authors.lastname: Charlier
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001124:Argininosuccinate Synthase / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009875:Operator Regions, Genetic / Q000502:physiology*; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020124:Thermotoga maritima / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C087018:ArgR protein, Bacteria; C490177:ArgR protein, E coli; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D000445:Aldehyde Oxidoreductases; C089846:argC protein, Bacteria; C474647:ArgG protein, E coli; D001124:Argininosuccinate Synthase