title: Triazole pyrimidine nucleosides as inhibitors of Ribonuclease A. Synthesis, biochemical, and structural evaluation.
abstract: Five ribofuranosyl pyrimidine nucleosides and their corresponding 1,2,3-triazole derivatives have been synthesized and characterized. Their inhibitory action to Ribonuclease A has been studied by biochemical analysis and X-ray crystallography. These compounds are potent competitive inhibitors of RNase A with low μM inhibition constant (K(i)) values with the ones having a triazolo linker being more potent than the ones without. The most potent of these is 1-[(β-D-ribofuranosyl)-1,2,3-triazol-4-yl]uracil being with K(i) = 1.6 μM. The high resolution X-ray crystal structures of the RNase A in complex with three most potent inhibitors of these inhibitors have shown that they bind at the enzyme catalytic cleft with the pyrimidine nucleobase at the B(1) subsite while the triazole moiety binds at the main subsite P(1), where P-O5' bond cleavage occurs, and the ribose at the interface between subsites P(1) and P(0) exploiting interactions with residues from both subsites. The effect of a susbsituent group at the 5-pyrimidine position at the inhibitory potency has been also examined and results show that any addition at this position leads to a less efficient inhibitor. Comparative structural analysis of these RNase A complexes with other similar RNase A-ligand complexes reveals that the triazole moiety interactions with the protein form the structural basis of their increased potency. The insertion of a triazole linker between the pyrimidine base and the ribose forms the starting point for further improvement of these inhibitors in the quest for potent ribonucleolytic inhibitors with pharmaceutical potential.
authors.affiliation: Department of Biochemistry and Biotechnology, University of Thessaly, 26 Ploutonos St., 41221 Larissa, Greece.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Parmenopoulou
authors.forename: Demetra S M
authors.initials: DS
authors.lastname: Chatzileontiadou
authors.forename: Stella
authors.initials: S
authors.lastname: Manta
authors.forename: Stamatina
authors.initials: S
authors.lastname: Bougiatioti
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Maragozidis
authors.forename: Dimitra-Niki
authors.initials: DN
authors.lastname: Gkaragkouni
authors.forename: Eleni
authors.initials: E
authors.lastname: Kaffesaki
authors.forename: Anastassia L
authors.initials: AL
authors.lastname: Kantsadi
authors.forename: Vassiliki T
authors.initials: VT
authors.lastname: Skamnaki
authors.forename: Spyridon E
authors.initials: SE
authors.lastname: Zographos
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Zounpoulakis
authors.forename: Nikolaos A A
authors.initials: NA
authors.lastname: Balatsos
authors.forename: Dimitris
authors.initials: D
authors.lastname: Komiotis
authors.forename: Demetres D
authors.initials: DD
authors.lastname: Leonidas
mesh_terms: D000818:Animals; D002417:Cattle; D018360:Crystallography, X-Ray; D015195:Drug Design; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D011487:Protein Conformation; D011741:Pyrimidine Nucleosides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D012259:Ribonuclease, Pancreatic / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D014230:Triazoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D011741:Pyrimidine Nucleosides; D014230:Triazoles; D012259:Ribonuclease, Pancreatic