Figure 2.

Deamination and binding assays with A3A and a 9-nt ssRNA. (A) Deamination of the single cytosine in the ssRNA oligonucleotide, AUUUCAUUU (JL1181, Table 1), was monitored by following the ¹³C-5-¹H resonances of cytosine and uracil in 2D ¹H-¹³C HSQC spectra. The total reaction time is indicated at the top right. Binding isotherms for representative HN resonances (B) and mapping of the binding site onto the A3A structure (C) for ssRNA (AUUUCAUUU) interacting with A3A, monitored by ¹H-¹⁵N HSQC spectroscopy. (D) Binding site of ssDNA ATTTCATTT mapped onto the A3A structure (16) for comparison. In (C) and (D), A3A residues whose resonances exhibit large ¹H,¹⁵N-combined chemical shift changes on nucleotide addition are colored red (> 0.05 p.p.m.) and orange (0.028–0.050 p.p.m.).