- Recognition of Artificial Nucleobases by E. coli Purine Nucleoside Phosphorylase versus its Ser90Ala Mutant in the Synthesis of Base-Modified Nucleosides
-
A wide range of natural purine analogues was used as probe to assess the mechanism of recognition by the wild-type (WT) E. coli purine nucleoside phosphorylase (PNP) versus its Ser90Ala mutant. The results were analyzed from viewpoint of the role of the Ser90 residue and the structural features of the bases. It was found that the Ser90 residue of the PNP 1) plays an important role in the binding and activation of 8-aza-7-deazapurines in the synthesis of their nucleosides, 2) participates in the binding of α-D-pentofuranose-1-phosphates at the catalytic site of the PNP, and 3) catalyzes the dephosphorylation of intermediary formed 2-deoxy-α-D-ribofuranose-1-phosphate in the trans-2-deoxyribosylation reaction. 5-Aza-7-deazaguanine manifested excellent substrate activity for both enzymes, 8-amino-7-thiaguanine and 2-aminobenzothiazole showed no substrate activity for both enzymes. On the contrary, the 2-amino derivatives of benzimidazole and benzoxazole are substrates and are converted into the N1- and unusual N2-glycosides, respectively. 9-Deaza-5-iodoxanthine showed moderate inhibitory activity of the WT E. coli PNP, whereas 9-deazaxanthine and its 2′-deoxyriboside are weak inhibitors. How does it work? The substrate and inhibitory properties of a wide range of artificial bases for the wild-type E. coli purine nucleoside phosphorylase (PNP) versus its Ser90Ala mutant were studied to evaluate the mechanism of recognition by PNP and the role of various electronic and structural features in this process. The PNP recognized a broad palette of bases consisting of a number of dissimilar fragments determining its ability to interact with the Asp204 and Ser90 residues (see scheme).
- Fateev, Ilja V.,Kharitonova, Maria I.,Antonov, Konstantin V.,Konstantinova, Irina D.,Stepanenko, Vasily N.,Esipov, Roman S.,Seela, Frank,Temburnikar, Kartik W.,Seley-Radtke, Katherine L.,Stepchenko, Vladimir A.,Sokolov, Yuri A.,Miroshnikov, Anatoly I.,Mikhailopulo, Igor A.
-
-
Read Online
- TLR8 activation and inhibition by guanosine analogs in RNA: Importance of functional groups and chain length
-
Toll-like receptor 8 (TLR8) is an important component of the human innate immune system that recognizes single stranded RNA (ssRNA). Recent X-ray crystal structures of TLR8 bound to ssRNA revealed a previously unrecognized binding site for a 5′-UpG-3′ dinucleotide. Here we use an atomic mutagenesis strategy coupled with a cellular TLR8 activation assay to probe the importance of specific functional groups present on the guanine base in RNA-mediated receptor agonism and antagonism. Results from RNA analogs containing 7-deazaguanosine, 2-aminopurine and inosine confirm the importance of guanine N7, O6 and N2, respectively, in TLR8 activation. Nevertheless, these RNAs each retained TLR8 antagonism activity. RNA containing 7-deaza-8-azainosine (7d8aI) was prepared from a novel phosphoramidite and found to be a weaker TLR8 activator than guanosine-containing RNA. However, 7d8aI-containing RNA also retained TLR8 antagonism activity indicating that removal of multiple TLR8 H-bonding sites on guanine is insufficient for blocking TLR8 antagonism by guanine-containing RNA. We also identified an oligoribonucleotide length dependence on both TLR8 activation and antagonism. These studies extend our understanding of the effects of nucleobase modification on immune stimulation and will inform the design of novel RNA-based therapeutics.
- Hu, Tiannan,Suter, Scott R.,Mumbleau, Madeline M.,Beal, Peter A.
-
-
Read Online
- Enzymatic Synthesis of 2-Deoxyribose 1-Phosphate and Ribose 1 Phosphate and Subsequent Preparation of Nucleosides
-
α-Ribose-1-phosphate (Rib-p) and 2-deoxy-α-ribose-1-phosphate (dRib-p) are key intermediates in nucleoside metabolism and are important starting compounds for the enzymatic synthesis of various modified nucleosides. To date, chemical and enzymatic methods allowed the preparation of these compounds in rather low yields (11–37 %). This prevents their widespread use for the enzymatic synthesis of biologically active and practically important nucleosides. Here we propose to use 7-methyl-2′-deoxyguanosine (7-Me-dGuo) and 7-methylguanosine (7-Me-Guo) for the preparation of dRib-p and Rib-p. In this paper, we present the effective preparation of Rib-p and dRib-p starting from readily prepared 7-methylguanosine derivatives via their irreversible enzymatic phosphorolysis in the presence of purine nucleoside phosphorylase. Rib-p and dRib-P are obtained in nearly quantitative yields (HPLC analysis) and 74–96 % yields after their isolation and purification, which is much higher than previously reported.
- Kulikova, Irina V.,Drenichev, Mikhail S.,Solyev, Pavel N.,Alexeev, Cyril S.,Mikhailov, Sergey N.
-
p. 6999 - 7004
(2019/11/13)
-
- Pyrazolo[3,4-d]pyrimidine ribonucleosides related to 2-aminoadenosine and isoguanosine: Synthesis, deamination and tautomerism
-
The syntheses and properties of 8-aza-7-deazapurine (pyrazolo[3,4-d] pyrimidine) ribonucleosides related to 2-aminoadenosine and isoguanosine are described. Glycosylation of 8-aza-7-deazapurine-2,6-diamine 5 with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribofur
- Seela, Frank,Xu, Kuiying
-
p. 3034 - 3045
(2008/04/01)
-
- Synthesis and biological activity of certain 3,4-disubstituted pyrazolo[3,4-d]pyrimidine nucleosides
-
A number of 3,4-disubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides were synthesized and tested for their biological activity. Glycosylation of persilylated as well as nonsilylated 3-bromoallopurinol with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose
- Cottam,Petrie,McKernan,Goebel,Dalley,Davidson,Robins,Revankar
-
p. 1119 - 1127
(2007/10/02)
-
- C4-substituted 1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidines as adenosine agonist analogues.
-
The synthesis of four novel C4-substituted 1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidines is reported, and the compounds were examined as adenosine receptor agonist analogues. Neither receptor affinity nor biological activity was as potent as the purine
- Hamilton,Bristol
-
p. 1601 - 1606
(2007/10/02)
-
- Pyrazolo[3,4-d]pyrimidine ribonucleosides as anticoccidials. II. Synthesis and activity of some nucleosides of 4-(alkylamino)-1H-pyrazolo[3,4-d]pyrimidines
-
A series of 4-(alkylamino)-1-β-D-ribofuranosyl-1H-pyrazolo[3,4-d]pyrimidines was synthesized by enzymatic and chemical methods. On the basis of the previous finding that 4-(alkylthio)-1-β-D-ribofuranosyl-1H-pyrazolo[3.4-d]pyrimidines were effective antico
- Rideout,Krenitsky,Koszalka,Cohn,Chao,Elion,Latter,Williams
-
p. 1040 - 1044
(2007/10/02)
-
