title: Molecular modeling and functional analysis of the AtoS-AtoC two-component signal transduction system of Escherichia coli.
abstract: The AtoS-AtoC two-component signal transduction system positively regulates the expression of the atoDAEB operon in Escherichia coli. Upon acetoacetate induction, AtoS sensor kinase autophosphorylates and subsequently phosphorylates, thereby activating, the response regulator AtoC. In a previous work we have shown that AtoC is phosphorylated at both aspartate 55 and histidine73. In this study, based on known three-dimensional structures of other two component regulatory systems, we modeled the 3D-structure of the receiver domain of AtoC in complex with the putative dimerization/autophosphorylation domain of the AtoS sensor kinase. The produced structural model indicated that aspartate 55, but not histidine 73, of AtoC is in close proximity to the conserved, putative phosphate-donor, histidine (H398) of AtoS suggesting that aspartate 55 may be directly involved in the AtoS-AtoC phosphate transfer. Subsequent biochemical studies with purified recombinant proteins showed that AtoC mutants with alterations of aspartate 55, but not histidine 73, were unable to participate in the AtoS-AtoC phosphate transfer in support of the modeling prediction. In addition, these AtoC mutants displayed reduced DNA-dependent ATPase activity, although their ability to bind their target DNA sequences in a sequence-specific manner was found to be unaltered.
authors.affiliation: Laboratory of Biochemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece.
authors.forename: A I
authors.initials: AI
authors.lastname: Grigoroudis
authors.forename: C A
authors.initials: CA
authors.lastname: Panagiotidis
authors.forename: E E
authors.initials: EE
authors.lastname: Lioliou
authors.forename: M
authors.initials: M
authors.lastname: Vlassi
authors.forename: D A
authors.initials: DA
authors.lastname: Kyriakidis
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D055672:Static Electricity
chemical_list: C505587:AtoC protein, E coli; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; C505586:AtoS protein, E coli; D000251:Adenosine Triphosphatases