Kinetic and mechanistic analyses of new classes of inhibitors of two-component signal transduction systems using a coupled assay containing HpkA-DrrA from Thermotoga maritima.
Two-component signal transduction systems (TCSs) play fundamental roles in bacterial survival and pathogenesis and have been proposed as targets for the development of novel classes of antibiotics. A new coupled assay was developed and applied to analyse the kinetic mechanisms of three new kinds of inhibitors of TCS function. The assay exploits the biochemical properties of the cognate HpkA-DrrA histidine kinase-response regulator pair from Thermotoga maritima and allows multiple turnovers of HpkA, linear formation of phosphorylated DrrA, and Michaelis-Menten analysis of inhibitors. The assay was validated in several ways, including confirmation of competitive inhibition by adenosine 5'-beta,gamma-imidotriphosphate (AMP-PNP). The coupled assay, autophosphorylation and chemical cross-linking were used to determine the mechanisms by which several compounds inhibit TCS function. A cyanoacetoacetamide showed non-competitive inhibition with respect to ATP concentration in the coupled assay. The cyanoacetoacetamide also inhibited autophosphorylation of histidine kinases from other bacteria, indicating that the coupled assay could detect general inhibitors of histidine kinase function. Inhibition of HpkA autophosphorylation by this compound was probably caused by aggregation of HpkA, consistent with a previous model for other hydrophobic compounds. In contrast, ethodin was a potent inhibitor of the combined assay, did not inhibit HpkA autophosphorylation, but still led to aggregation of HpkA. These data suggest that ethodin bound to the HpkA kinase and inhibited transfer of the phosphoryl group to DrrA. A peptide corresponding to the phosphorylation site of DrrA appeared to inhibit TCS function by a mechanism similar to that of ethodin, except that autophosphorylation was inhibited at high peptide concentrations. The latter mechanism of inhibition of TCS function is unusual and its analysis demonstrates the utility of these approaches to the kinetic analyses of additional new classes of inhibitors of TCS function.
Foster
J Estelle
JE
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Sheng
Qin
Q
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
McClain
Jonathan R
JR
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Bures
Mark
M
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Nicas
Thalia I
TI
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Henry
Kenneth
K
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Winkler
Malcolm E
ME
Department of Biology, Indiana University, Bloomington, IN, 47405, USA.|Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
Gilmour
Raymond
R
Lilly Research Laboratories, Eli Lilly and Company, Drop Code 0428, Lilly Corporate Center, Indianapolis IN 46285, USA.
D000090:Acetoacetates / Q000737:chemistry / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D000577:Amides / Q000737:chemistry / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004975:Ethacridine / Q000494:pharmacology; D000071677:Histidine Kinase; D007700:Kinetics; D009570:Nitriles / Q000737:chemistry / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020124:Thermotoga maritima / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology
D000090:Acetoacetates; D000577:Amides; D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C101895:DrrA protein, Bacteria; C487547:N-(4-(4-tert-butylphenyl)thiazol-2-yl)-N-propyl-2-cyano-3-hydroxy-2-butenamide; D009570:Nitriles; D010455:Peptides; D047428:Protein Kinase Inhibitors; D013844:Thiazoles; D000266:Adenylyl Imidodiphosphate; D011494:Protein Kinases; D000071677:Histidine Kinase; D004975:Ethacridine; C031594:2-cyanoacetamide