- Synthesis of cyclic adenosine 5′-diphosphate ribose analogues: A C2′ endo/syn "southern" ribose conformation underlies activity at the sea urchin cADPR receptor
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Novel 8-substituted base and sugar-modified analogues of the Ca 2+ mobilizing second messenger cyclic adenosine 5′-diphosphate ribose (cADPR) were synthesized using a chemoenzymatic approach and evaluated for activity in sea urchin egg homogenate (SUH) and in Jurkat T-lymphocytes; conformational analysis investigated by 1H NMR spectroscopy revealed that a C2′ endo/syn conformation of the "southern" ribose is crucial for agonist or antagonist activity at the SUH-, but not at the T cell-cADPR receptor.
- Moreau, Christelle,Ashamu, Gloria A.,Bailey, Victoria C.,Galione, Antony,Guse, Andreas H.,Potter, Barry V. L.
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experimental part
p. 278 - 290
(2011/02/23)
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- RImN and Cfr are Radical SAM Enzymes Involved in Methylation of Ribosomal RNA
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Posttranscriptional modifications of ribosomal RNA (rRNA) nucleotides are a common mechanism of modulating the ribosome's function and conferring bacterial resistance to ribosome-targeting antibiotics. One such modification is methylation of an adenosine nucleotide within the peptidyl transferase center of the ribosome mediated by the endogenous methyltransferase RImN and its evolutionarily related resistance enzyme Cfr. These methyltransferases catalyze methyl transfer to aromatic carbon atoms of the adenosine within a complex 23S rRNA substrate to form the 2,8-dimethylated product. RImN and Cfr are members of the Radical SAM superfamily and contain the characteristic cysteine-rich CX3CX2C motif. We demonstrate that both enzymes are capable of accommodating the requisite [4Fe-4S] cluster. S-Adenosylmethionine (SAM) is both the methyl donor and the source of a 5′-deoxyadenosyl radical, which activates the substrate for methylation. Detailed analyses of the rRNA requirements show that the enzymes can utilize proteinfree 23S rRNA as a substrate, but not the fully assembled large ribosomal subunit, suggesting that the methylations take place during the assembly of the ribosome. The key recognition elements in the 23S rRNA are helices 90-92 and the adjacent single stranded RNA that encompasses A2503. To our knowledge, this study represents the first in vitro description of a methyl transfer catalyzed by a member of the Radical SAM superfamily, and it expands the catalytic repertoire of this diverse enzyme class. Furthermore, by providing information on both the timing of methylation and its substrate requirements, our findings have important implications for the functional consequences of Cfr-mediated modification of rRNA in the acquisition of antibiotic resistance.
- Yan, Feng,Lamarre, Jacqueline M.,Roehrich, Rene,Wiesner, Jochen,Jomaa, Hassan,Markin, Alexander S.,Fujimori, Danica Galonic
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scheme or table
p. 3953 - 3964
(2010/05/15)
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- New insights into the design of inhibitors of human S-adenosylmethionine decarboxylase: studies of adenine C8 substitution in structural analogues of S-adenosylmethionine
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S-Adenosylmethionine decarboxylase (AdoMetDC) is a critical enzyme in the polyamine biosynthetic pathway and depends on a pyruvoyl group for the decarboxylation process. The crystal structures of the enzyme with various inhibitors at the active site have shown that the adenine base of the ligands adopts an unusual syn conformation when bound to the enzyme. To determine whether compounds that favor the syn conformation in solution would be more potent AdoMetDC inhibitors, several series of AdoMet substrate analogues with a variety of substituents at the 8-position of adenine were synthesized and analyzed for their ability to inhibit hAdoMetDC. The biochemical analysis indicated that an 8-methyl substituent resulted in more potent inhibitors, yet most other 8-substitutions provided no benefit over the parent compound. To understand these results, we used computational modeling and X-ray crystallography to study C8-substituted adenine analogues bound in the active site.
- McCloskey, Diane E.,Bale, Shridhar,Secrist III, John A.,Tiwari, Anita,Moss III, Thomas H.,Valiyaveettil, Jacob,Brooks, Wesley H.,Guida, Wayne C.,Pegg, Anthony E.,Ealick, Steven E.
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scheme or table
p. 1388 - 1407
(2009/12/07)
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- INHIBITORS OF S-ADENOSYL-L-METHIONINE DECARBOXYLASE
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Novel mechanism-based inhibitors of S-adenosyl-L-methionine decarboxylase are provided. These compounds of formula (1) inhibit the life cycle of trypanosomes, and are useful to treat subjects infected with African trypanosomes. The invention includes pharmaceutical compositions and methods of using the compounds of formula (1).
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Page/Page column 12; 21-22
(2009/01/23)
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- PURINE NUCLEOTIDE DERIVATIVES
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This invention provides novel 8-carbyl substituted cAMPS and a novel procedures for the preparation of 8-Br-cAMP, a key starting material.
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Page/Page column 21; 58
(2010/02/15)
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- Antiviral Activity of C-Alkylated Purine Nucleosides Obtained by Cross-Coupling with Tetraalkyltin Reagents
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2-, 6-, And 8-alkylated (methyl, ethyl, and vinyl) adenosine analogues were synthesized by a palladium-catalyzed cross-coupling of a tetraalkyltin with the halogenated purine nucleosides.The synthesis of the 8-substituted analogues was accomplished using a transient protection procedure.The 6-alkylated-9-β-D-ribofuranosylpurines as well as 2-ethyladenosine were cytotoxic at relatively low concentrations (0.8-10 μg/mL). 8-Methyladenosine was a potent and selective inhibitor of vaccinia virus, whereas 8-ethyl- and 8-vinyladenosine were specifically inhibitory to respiratory syncytial virus. 8-Vinyladenosine displayed particular activity against herpes simplex virus (type 1).
- Aerschot, Arthur A. Van,Mamos, Petros,Weyns, Nancy J.,Ikeda, Satoru,Clercq, Erik De,Herdewijn, Piet A.
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p. 2938 - 2942
(2007/10/02)
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- Straightforward C-8 alkylation of adenosine analogues with tetraalkyltin reagents
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A one step synthesis of the 8-methyl-, 8-ethyl- and 8-vinyl derivatives of adenosine, 2'-deoxyadenosine and 2',3'-dideoxyadenosine starting from the readily available 8-bromo congeners is described. This reaction makes use of a transient silylation procedure and a Pd(0) catalysed cross-coupling with tetraorganotin reagents.
- Mamos,Van Aerschot,Weyns,Herdewijn
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p. 2413 - 2416
(2007/10/02)
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- Unusual Competition between Nitrogen and Carbon Methylation of Nucleosides by Methyl Radical in Various Aqueous Media
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Five nucleosides, adenosine, guanosine, cytidine, thymidine, and uridine, were allowed to react with methyl radical produced by homolysis of tert-butyl peracetate.The extent and sites of reaction exhibited a marked dependence on the pH of the aqueous medium.In the region of pH 1-4, the major products arose from C-methylation of the nucleosides.The purines were more reactive than the pyrimidines under these acidic conditions.In the pH range of 4-10, the extent of C-methylation decreased steadily with increasing pH while N-methylated products arising from methylationof the ring nitrogen and/or exocyclic amino groups predominated.In this pH range, the pyrimidine nucleosides were the more reactive.Beyond pH 10, the extent of methylation diminished in all cases as decomposition of tert-butyl peracetate became rampant.The C-methylation occurs by way of an addition mechanism while N-methylation appears to proceed via radical abstraction of a hydrogen from the N-H group followed by combination with methyl radical.The implications of these reactivity and methylation patterns in radical carcinogenesis are discussed.
- Zady, Mona F.,Wong, John L.
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p. 2373 - 2377
(2007/10/02)
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