Substrate analogues for an RNA-editing adenosine deaminase: Mechanistic investigation and inhibitor design

Eduardo A. Véliz, LaHoma M. Easterwood, Peter A. Beal

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


ADARs are adenosine deaminases that act on RNA and are responsible for RNA-editing reactions that occur in eukaryotic mRNAs, including the mRNAs of glutamate and serotonin receptors. ADARs capable of editing biologically relevant RNA substrates have been identified. In addition, the consequence of the RNA-editing reaction on the function of the gene product is known in several cases. However, our understanding of the chemical mechanism of the ADAR-catalyzed adenosine deamination in RNA is lagging. By studying analogues of a naturally occurring substrate for ADAR2, we infer features of the enzyme's active site and reaction mechanism. 8-Aza substitution at adenosine in various RNA substrates accelerates the rate of deamination at these sites by ADAR2 (2.8-17-fold). The magnitude of this "aza effect" depends on the RNA structural context of the reacting nucleotide. N6-Methyladenosine in RNA is a slow substrate for ADAR2 (rate is 2% that of adenosine), with no product observed with N6-ethyladenosine, suggesting a limited size of the leaving group pocket. 2,6-Diaminopurine ribonucleoside in RNA is not a substrate for ADAR, in contrast to adenosine deaminase (ADA), which catalyzes a similar reaction on nucleosides. This and other results indicate that ADAR2 uses a base recognition strategy different from that of ADA. Consistent with the large 8-aza effect observed for the ADAR2 reaction, we find that 8-azanebularine, as the free nucleoside, inhibits the ADAR2 reaction (IC 50 = 15 ± 3 mM) with no inhibition observed with nebularine or coformycin.

Original languageEnglish (US)
Pages (from-to)10867-10876
Number of pages10
JournalJournal of the American Chemical Society
Issue number36
StatePublished - Sep 10 2003
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)


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