Fig. 4: Comparison of T-1105-RTP:U and natural GTP:U mismatch incorporation levels.

a Elongation reactions with the PT substrate done in the absence of ATP with 50 µM each GTP, UTP and CTP show rapid addition of the first uracil followed by slow misincorporation of a GTP:U mismatch. In the presence of 1 µM T-1105-RTP (with 50 µM each GTP, UTP and CTP) the analogue incorporation is on a similar timescale as the native GTP:U mismatch. b Analysis of incorporation levels show a burst phase followed by linear product buildup over a 60-s timeframe that is consistent with the measured lifetime of the nsp12-7L8-8 elongation complex. Both the burst amplitude and linear rate indicate that 1 µM T-1105-RTP is incorporated ~5-fold faster than the natural GTP:U mismatch at 50 µM GTP. Quantitation reflects slopes and intercepts with standard errors obtained from a linear curve fit to the initial rate data (0–60 s). Expanded concentration series shown in Supplementary Fig. 5b, bottom panel. Source data are provided as a Source Data file.