title: Metal-1,4-dithio-2,3-dihydroxybutane chelates: novel inhibitors of the Rho transcription termination factor.
abstract: Rho is an enzyme that is essential for the growth and survival of Escherichia coli, and bicyclomycin (1) is its only known selective inhibitor. We show that metal (Cd(2+), Ni(2+), and Zn(2+)) complexes of 1,4-dithio-2,3-dihydroxybutanes (2) serve as effective and potent rho inhibitors with I(50) values that can exceed that of 1. Maximal inhibition for ZnCl(2) and L-dithiothreitol (2a) corresponded to Zn(2):L-DTT stoichiometry. The I(50) value for the 2:1 Zn-L-DTT solution was 20 microM, which made it 3 times more potent than 1 (I(50) = 60 microM). Kinetic studies showed that a Zn-L-DTT solution functioned as a noncompetitive inhibitor with respect to ATP in the rho poly(C)-dependent ATPase assay and as a competitive inhibitor with respect to ribo(C)(10) in the poly(dC).ribo(C)(10)-stimulated ATPase assay. These findings demonstrated that both 1 and a Zn-L-DTT solution disrupted rho-mediated ATP hydrolysis but that they inhibit using different mechanisms. Substitution of L-DTT with 1,2-ethanedithiol in ZnCl(2) solutions led to a comparable loss of rho poly(C)-dependent ATPase activity, indicating that other metal chelates can serve as efficient inhibitors. The site and pathway of rho inhibition by the putative metal-1,4-dithio-2,3-dihydroxybutane chelates are discussed in light of the current data.
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204-5641, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Weber
authors.forename: William R
authors.initials: WR
authors.lastname: Widger
authors.forename: Harold
authors.initials: H
authors.lastname: Kohn
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D019256:Cadmium Chloride / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D004229:Dithiothreitol / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry; D011066:Poly C / Q000737:chemistry; D012234:Rho Factor / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D012996:Solutions; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D002614:Chelating Agents; D002712:Chlorides; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D017895:Manganese Compounds; D019216:Metals, Heavy; D012234:Rho Factor; D012996:Solutions; D017967:Zinc Compounds; D011066:Poly C; C022838:nickel chloride; D009532:Nickel; C016837:zinc chloride; D000251:Adenosine Triphosphatases; C024504:bicozamycin; D019256:Cadmium Chloride; C025340:manganese chloride; D004229:Dithiothreitol