title: The DNA-binding domain of the hexameric arginine repressor.
abstract: The arginine repressor of Escherichia coli is a classical feedback regulator, signalling the availability of L-arginine inside the cell. It differs from most other bacterial repressors in functioning as a hexamer, but structural details have been lacking and its shares no clear sequence homologies with other transcriptional regulators. Analysis of the amino acid residue sequence and proteolytic cleavage pattern of the repressor was used to identify a region predicted to house the DNA-binding function. When this protein fragment is overexpressed from a clone of the corresponding gene fragment, it represses ornithine transcarbamylase levels in vivo, and binds to the operator DNA in vitro, both in an arginine-independent manner. Sedimentation equilibrium and gel filtration indicate that the purified protein fragment is a monomer in solution. The results thus define the domain organization of the repressor at low resolution, suggesting that the N and C-terminal portions of the polypeptide chain are separated by a structural and functional border that decouples hexamerization and arginine binding from DNA binding.
mesh_terms: D000494:Allosteric Regulation / Q000235:genetics; D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins; D001483:Base Sequence; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D004794:Enzyme Repression; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009875:Operator Regions, Genetic; D009954:Ornithine Carbamoyltransferase / Q000096:biosynthesis / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic; D014357:Trypsin / 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; D010446:Peptide Fragments; D012097:Repressor Proteins; D007544:Isopropyl Thiogalactoside; D001120:Arginine; D009954:Ornithine Carbamoyltransferase; D002918:Chymotrypsin; D014357:Trypsin