Structural Analysis of the Activation of Ribavirin Analogs by NDP Kinase: Comparison with Other Ribavirin Targets

Abstract

Ribavirin used in therapies against hepatitis C virus (HCV) is potentially efficient against other viruses but presents a high cytotoxicity. Several ribavirin triphosphate analogs modified on the ribose moiety were synthesized and tested in vitro on the RNA polymerases of HCV, phage T7, and HIV-1 reverse transcriptase. Modified nucleotides with 2Ј-deoxy, 3Ј-deoxy, 2Ј,3Ј-dideoxy, 2Ј,3Ј-dideoxy-2Ј,3Ј-dehydro, and 2Ј,3Ј-epoxy-ribose inhibited the HCV enzyme but not the other two polymerases. They were also analyzed as substrates for nucleoside diphosphate (NDP) kinase, the enzyme responsible for the last step of the cellular activation of antiviral nucleoside analogs. An X-ray structure of NDP kinase complexed with ribavirin triphosphate was determined. It demonstrates that the analog binds as a normal substrate despite the modified base and confirms the crucial role of the 3Ј-hydroxyl group in the phosphorylation reaction. The 3Ј-hydroxyl is required for inhibition of the initiation step of RNA synthesis by HCV polymerase, and both sugar hydroxyls must be present to inhibit elongation. The 2Јde-oxyribavirin is the only derivative efficient in vitro against HCV polymerase and properly activated by NDP kinase.

Human uridine-cytidine kinase phosphorylation of ribavirin: a convenient method for activation of ribavirin for conjugation to proteins

“…Resistance to the effect of ribavirin on purine excretion was associated only with those cell lines deficient in adenosine kinase activity, and therefore adenosine kinase has been implicated to be responsible for ribavirin phosphorylation [26]. Nucleoside diphosphate kinases and other kinases of the salvage nucleotide pathway have also been implicated to be responsible for ribavirin phosphorylation [27,28]. Our data support the notion that ribavirin is a potential substrate of UCK-1.…”

Identification of a nucleoside analog active against adenosine kinase–expressing plasma cell malignancies

“…The latter possibility is supported by previous data indicating that ADK can activate other nucleoside analogs, including several important antiviral compounds such as ribavirin (20)(21)(22), triciribine (23), mizoribine (24), and tiazofurin (25), although these compounds can also be activated by a variety of other kinases (26). Such a model was also supported by the locations of the observed mutations, one at and one near the active site of the enzyme, suggesting the involvement of such interactions in drug activity.…”

Effects of Mutagenic and Chain-Terminating Nucleotide Analogs on Enzymes Isolated from Hepatitis C Virus Strains of Various Genotypes

“…A third proposed antiviral mechanism is direct inhibition of the NS5B polymerase. Cellular kinases convert RMP to ribavirin diphosphate (RDP) and ribavirin triphosphate (RTP) (22). RTP acts as a competitive inhibitor of viral replication; once incorporated, it presents a significant block to RNA elongation and is a poor template for RNA synthesis.…”