The design and synthesis of redox core-alpha amino acid composites based on thiol-disulfide exchange mechanism and a comparative study of their zinc abstraction potential from [CCXX] boxes in proteins
TL;DR: In this paper, the authors showed that the removal of the exchangeable zinc atoms in the [CCXX] boxes of E. coli RNA polymerase can be achieved by using thioldisulfide exchange-having as a control.
Abstract: The design and synthesis of agents that can abstract zinc from their [CCXX] (C=cysteine; X=cysteine/histidine) boxes by thioldisulfide exchange-having as control, the redox parities of the core sulfur ligands of the reagent and the enzyme, has been illustrated, and their efficiency demonstrated by monitoring the inhibition of the transcription of calf thymus DNA by E. coli RNA polymerase, which harbors two zinc atoms in their [CCXX] boxes of which one is exchangeable. Maximum inhibition possible with removal of the exchangeable zinc was seen with redox-sulfanilamide-glutamate composite. In sharp contrast, normal chelating agents (EDTA, phenanthroline) even in a thousand fold excess showed only marginal inhibition, thus supporting an exchange mechanism for the metal removal. (C) 2002 Elsevier Science Ltd. All rights reserved.
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TL;DR: EbS, a sulfur analogue of ebselen, is a potent inhibitor of T. brucei growth with a favorable selectivity index over mammalian cells and is a promising lead for development of drugs against African trypanosomiasis.
Abstract: Trypanosoma brucei is the causing agent of African trypanosomiasis. These parasites possess a unique thiol redox system required for DNA synthesis and defense against oxidative stress. It includes trypanothione and trypanothione reductase (TryR) instead of the thioredoxin and glutaredoxin systems of mammalian hosts. Here, we show that the benzisothiazolone compound ebsulfur (EbS), a sulfur analogue of ebselen, is a potent inhibitor of T. brucei growth with a favorable selectivity index over mammalian cells. EbS inhibited the TryR activity and decreased non-protein thiol levels in cultured parasites. The inhibition of TryR by EbS was irreversible and NADPH-dependent. EbS formed a complex with TryR and caused oxidation and inactivation of the enzyme. EbS was more toxic for T. brucei than for Trypanosoma cruzi, probably due to lower levels of TryR and trypanothione in T. brucei. Furthermore, inhibition of TryR produced high intracellular reactive oxygen species. Hydrogen peroxide, known to be constitutively high in T. brucei, enhanced the EbS inhibition of TryR. The elevation of reactive oxygen species production in parasites caused by EbS induced a programmed cell death. Soluble EbS analogues were synthesized and cured T. brucei brucei infection in mice when used together with nifurtimox. Altogether, EbS and EbS analogues disrupt the trypanothione system, hampering the defense against oxidative stress. Thus, EbS is a promising lead for development of drugs against African trypanosomiasis.
48 citations
Additional excerpts
...Compound Synthesis and Analysis—Compounds 1 (30), 2 (31), 3 (31), 4 (27), 5 (27), 6 (31), 7 (31), 8 (31), 9 (31), 10 (32), 11 (27, 33), 12 (27), 13 (34), 14 (35), 18 (36), and 19 (36) were prepared according to literature methods....
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TL;DR: One-pot synthesis of N-substituted benzo[d]isothiazol-3(2H)-ones using copper-catalysis from 2-halobenzamides and sulfur powder via C-S/N-S bond formation with high yield is described in this paper.
Abstract: One-pot synthesis of N-substituted benzo[d]isothiazol-3(2H)-ones has been described using copper-catalysis from N-substituted 2-halobenzamides and sulfur powder via C-S/N-S bond formation with high yield.
24 citations
TL;DR: In this paper, a synthesis and antimicrobial evaluation of some typical macrocyclic crown ethers including amide, sulfonamide, and disulfide moieties is reported.
Abstract: Synthesis and antimicrobial evaluation of some typical macrocyclic crown ethers including amide, sulfonamide, and disulfide moieties are reported. Novel macrocyclic bis -sulfonamide, amide, and disulfides are prepared by reacting the bis -chlorides and diamines by fast addition method. The antimicrobial activities of the synthesized compounds are measured. Bis -sulfonamide and disulfide crown ethers showed antibacterial activities against most strains tested.
23 citations
TL;DR: In this article, a cyclic bis-disulfide was selectively prepared by iodine oxidation of the Ni complex of a pseudopeptidic cyclic disulfide and its crystal structure was solved by X-ray diffraction.
Abstract: Twelve-membered ring pseudopeptidic cyclic disulfides have been prepared by iodine oxidation of the parent dithiols. However, oxidation of N,N′-(1,2-phenylene)bis(2-mercapto-2-methylpropanamide) afforded a 25/75 mixture of cyclic mono- and bis-disulfides that were separated by selective precipitation in CHCl3. The cyclic bis-disulfide was selectively prepared by iodine oxidation of the Ni complex of this dithiol and crystallized. Its crystal structure was solved by X-ray diffraction. All these cyclic mono- or bis-disulfides were selectively converted to cyclic mono- and bis-thiosulfinates upon stoichiometric oxidation with dimethyldioxirane at low temperature. 1H NMR of the cyclic bis-thiosulfinate revealed the presence of four isomers, two couples of stereoisomers, as expected from the insertion of two oxygen atoms in this compound, one on each disulfide bond. The two couples of cis/trans isomers were separated by preparative TLC and identified after alkaline cleavage of the two S(O)–S bonds and metalation with Ni(II). As HO− attack is selective for the sulfinyl sulfur, the nature of the Ni complexes obtained is a signature of each couple of stereoisomers.
20 citations
TL;DR: A novel reaction pathway involving 1,3-diketones and 2,2'-dithiodibenzoylchloride that gives access to benzothiophenes with spiroketal, lactone, carbonyl, hydroxyl and carboxylic acid functionalities is discussed.
Abstract: A novel reaction pathway involving 1,3-diketones and 2,2′-dithiodibenzoylchloride that gives access to benzothiophenes with spiroketal, lactone, carbonyl, hydroxyl and carboxylic acid functionalities is discussed.
17 citations
References
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TL;DR: The ability of zinc to be bound specifically within a range of tetrahedral sites appears to be responsible for the evolution of the wide range of zinc-stabilized structural domains now known to exist.
Abstract: Zinc ions are key structural components of a large number of proteins. The binding of zinc stabilizes the folded conformations of domains so that they may facilitate interactions between the proteins and other macromolecules such as DNA. The modular nature of some of these zinc-containing proteins has allowed the rational design of site-specific DNA binding proteins. The ability of zinc to be bound specifically within a range of tetrahedral sites appears to be responsible for the evolution of the side range of zinc-stabilized structural domains now known to exist. The lack of redox activity for the zinc ion and its binding and exchange kinetics also may be important in the use of zinc for specific functional roles.
1,801 citations
TL;DR: The X-ray crystal structure of Thermus aquaticus core RNA polymerase reveals a "crab claw"-shaped molecule with a 27 A wide internal channel that places key functional sites, defined by mutational and cross-linking analysis, on the inner walls of the channel in close proximity to the active center Mg2+.
Abstract: Summary 1960) and the isolation of the RNAP enzyme from bacte- rial sources (Chamberlin and Berg, 1962), a wealth of The X-ray crystal structure of Thermus aquaticus core biochemical, biophysical, and genetic information hasRNA polymerase reveals a “crab claw”–shaped mole- accumulated on RNAP and its complexes with nucleic cule with a 27 A˚ wide internal channel. Located on the acids and accessory factors (von Hippel et al., 1984; back wall of the channel is a Mg 2 1 ion required for Erie et al., 1992; Sentenac et al., 1992; Gross et al., catalytic activity, which is chelated by an absolutely 1996). Nevertheless, the enzyme itself, in terms of its conserved motif from all bacterial and eukaryotic cel- structure–function relationship, remains a black box. An lularRNApolymerases.The structureplaceskeyfunc- essential step toward understanding the mechanism of tional sites, defined by mutational and cross-linking transcription and its regulation is to determine three- analysis, on the inner walls of the channel in close
814 citations
TL;DR: Nontoxic disulfide-substituted benzamides were identified that attack the zinc fingers, inactivate cell-free virions, inhibit acute and chronic infections, and exhibit broad antiretroviral activity.
Abstract: Strategies for the treatment of human immunodeficiency virus-type 1 (HIV-1) infection must contend with the obstacle of drug resistance. HIV-1 nucleocapsid protein zinc fingers are prime antiviral targets because they are mutationally intolerant and are required both for acute infection and virion assembly. Nontoxic disulfide-substituted benzamides were identified that attack the zinc fingers, inactivate cell-free virions, inhibit acute and chronic infections, and exhibit broad antiretroviral activity. The compounds were highly synergistic with other antiviral agents, and resistant mutants have not been detected. Zinc finger-reactive compounds may offer an anti-HIV strategy that restricts drug-resistance development.
278 citations
TL;DR: These experiments demonstrate that zinc finger DNA-binding domains can be engineered de novo to recognise given DNA sequences and are sufficiently long to constitute a rare address in the human genome.
Abstract: Zinc fingers are small DNA-binding peptide motifs that were discovered in this laboratory. These motifs can be used as modular building blocks for the construction of larger protein domains that recognise and bind to specific DNA sequences. Phage display has been used to create a large library of different zinc fingers from which selections were made for binding to a given DNA sequence. From this database there have been elucidated elements of recognition rules that relate the amino acid sequence of a finger to its preferred DNA binding site. Control of gene expression using designed zinc finger peptides has been demonstrated by the specific inhibition of an oncogene mouse cell line and also by switching on genes in expression plasmids. These experiments demonstrate that zinc finger DNA-binding domains can be engineered de novo to recognise given DNA sequences. Five to six individual zinc fingers linked together would recognise a DNA sequence 15-18 bp in length, sufficiently long to constitute a rare address in the human genome. By adding functional groups to the engineered DNA-binding domains, e.g. silencing domains, novel transcription factors can be generated to up- or downregulate expression of a target gene. Among potential applications are the repression of oncogene expression and the disruption of the reproductive cycle of virus infection.
240 citations
TL;DR: The structural findings provide a rationalization for the general conservation of these hydrophobic and basic residues in CCHC zinc fingers, and are consistent with site‐directed mutagenesis results that implicate these residues as direct participants in viral genome recognition.
Abstract: The nucleic acid interactive properties of a synthetic peptide with sequence of the N-terminal CCHC zinc finger (CCHC = Cys-X2-Cys-X4-His-X4-Cys; X = variable amino acid) of the human immunodeficiency virus (HIV) nucleocapsid protein, Zn(HIV1-F1), have been studied by 1H NMR spectroscopy. Titration of Zn(HIV1-F1) with oligodeoxyribonucleic acids containing different nucleotide sequences reveals, for the first time, sequence-dependent binding that requires the presence of at least one guanosine residue for tight complex formation. The dynamics of complex formation are sensitive to the nature of the residues adjacent to guanosine, with residues on the 3' side of guanosine having the largest influence. An oligodeoxyribonucleotide with sequence corresponding to a portion of the HIV-1 psi-packaging signal, d(ACGCC), forms a relatively tight complex with Zn(HIV1-F1) (Kd = 5 x 10(-6) M). Two-dimensional nuclear Overhauser effect (NOESY) data indicate that the bound nucleic acid exists predominantly in a single-stranded, A-helical conformation, and the presence of more than a dozen intermolecular NOE cross peaks enabled three-dimensional modeling of the complex. The nucleic acid binds within a hydrophobic cleft on the peptide surface. This hydrophobic cleft is defined by the side chains of residues Val1, Phe4, Ile12, and Ala13. Backbone amide protons of Phe4 and Ala13 and the backbone carbonyl oxygen of Lys2 that lie within this cleft appear to form hydrogen bonds with the guanosine O6 and N1H atoms, respectively. In addition, the positively charged side chain of Arg14 is ideally positioned for electrostatic interactions with the phosphodiester backbone of the nucleic acid. The structural findings provide a rationalization for the general conservation of these hydrophobic and basic residues in CCHC zinc fingers, and are consistent with site-directed mutagenesis results that implicate these residues as direct participants in viral genome recognition.
119 citations