title: Asymmetric allosteric activation of the symmetric ArgR hexamer.
abstract: Hexameric arginine repressor, ArgR, bound to L-arginine serves both as the master transcriptional repressor/activator at diverse regulons in a wide range of bacteria and as a required cofactor for resolution of ColE1 plasmid multimers. Multifunctional ArgR is thus unusual in possessing features of specific gene regulators, global regulators, and non-specific gene organizers; its closest functional analog is probably CAP, the cyclic AMP receptor/activator protein. Isothermal titration calorimetry, surface plasmon resonance, and proteolysis indicate that binding of a single L-argine [corrected] per ArgR hexamer triggers a global conformation [corrected] change and resets the affinities of the remaining five sites, making them 100-fold weaker. The analysis suggests a novel thermodynamic signature for this mechanism of activation.
authors.affiliation: Chemistry Department, DePaul University, Chicago, IL 60614, USA. ljin@depaul.edu
authors.forename: Lihua
authors.initials: L
authors.lastname: Jin
authors.forename: Wei-Feng
authors.initials: WF
authors.lastname: Xue
authors.forename: June Wong
authors.initials: JW
authors.lastname: Fukayama
authors.forename: Jaclyn
authors.initials: J
authors.lastname: Yetter
authors.forename: Michael
authors.initials: M
authors.lastname: Pickering
authors.forename: Jannette
authors.initials: J
authors.lastname: Carey
mesh_terms: D000494:Allosteric Regulation; D001120:Arginine / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002151:Calorimetry; D010447:Peptide Hydrolases / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D020349:Surface Plasmon Resonance; D017186:Titrimetry
chemical_list: C087018:ArgR protein, Bacteria; D001426:Bacterial Proteins; D012097:Repressor Proteins; D001120:Arginine; D010447:Peptide Hydrolases