189887-75-0Relevant articles and documents
Inhibition of hepatitis C viral RNA-dependent RNA polymerase by α-P-boranophosphate nucleotides: Exploring apotential strategy for mechanism-based HCV drug design
Cheek, Marcus Adrian,Sharaf, Mariam L.,Dobrikov, Mikhail I.,Shaw, Barbara Ramsay
, p. 144 - 152 (2013/08/23)
Improved treatments for chronic HCV infections remain a challenge,and new chemical strategies are needed to expand the current paradigm. The HCV RNA polymerase (RdRP) has been a target for antiviral development. For the first time we show that the boranophosphate (BP)modification increases the sub-strate efficiency of ATP analogs into HCV NS5B Δ55 RdRP-catalyzed RNA. Boranophosphate nucleotides contain a borane (BH3) group substituted for anon-bridging phosphoryl oxygen of a normal phosphate group, resulting in a class of modified isoelectronic DNA and RNA mimics capable of modulating the reading and writing of genetic information. We determine that HCV NS5B Δ55, being a stereo specific enzyme, incorporates the Rp isomer of both ATP αB and the two boranophos phate analogs:2'-O-methyladenosine5'-(α-P-borano) triphosp hate (2'-OMe ATP αB, 5a) and 3'-deoxyadenosine 5'-(α-P-borano) triphosphate(3'-dATPaB, 5b). The Rp3 diastereomer of ATP αB (6), having noribose modifications, was found to be a slightly better substrate than natural ATP, showing a42%decrease inthe apparent Michaelis-Mentenconstan t (Km). The IC50 of both 2'-O-Me and 3'-deoxy ATP was decreased with the boranophosphate modification upto16-fold. This ''borano effect''was further confirmed by determining the steady-state in hibitory constant (Ki), showing a comparable potency shift (21-fold). These experiments also indicate that the boranophosphat eanalogs 5a and 5b inhibit HCV NS5B through a competitiv emode of inhibition. This evidence, together with previous crystal structure data, further supports the idea that HCV NS5B (in a similar manner toHIV-1 RT)discriminates against the 3'-deoxy modification via lost interactions between the 3'-OH on the ribose and the active site residues, or lost intramolecular hydrogen bonding interactions between the 3'-OH and the pyrophosphate leaving group during phosphoryl transfer. To our knowledge, these data represent the first time a phosphate modified NTP has been studied as a sub-strate for HCV NS5B RdRP.
