Fidelity of base-pair recognition by a 3′–5′ polymerase: mechanism of the Saccharomyces cerevisiae tRNA^His guanylyltransferase

Single-turnover measurement of nucleotidyl transfer with GTP analogs and full-length 5′ppp-tRNA^His substrates. (A) Chemical structures of selected analogs tested in nucleotidyl transfer reactions. Differences from standard GTP nucleotides are highlighted with red circles on each diagram; R indicates ribose 5′-triphosphate. (B) Single-turnover rate (k_obs) of nucleotidyl transfer was measured using the 5′-*ppp-tRNA^His substrate (as indicated) in the presence of 1 mM of each GTP analog [GTP (red), ITP (green), 2APTP (blue), 7-deaza-GTP (orange) and 8-oxo-GTP (black)] and 15 µM SceThg1.