Figure 4.

2′,3′-CPDase activity of RtcB H337A. The H337A mutant was reacted with the _HORNA > p substrate in the presence of 0.1 mM GTP (+GTP) or in the absence of added nucleotide (−GTP) as described in Figure 2. The abundance of the 3′-phosphate-terminated T1 fragment _HOCUUpCp, expressed as the percent of the total radiolabeled material, is plotted as a function of reaction time. Each datum is the average of three independent experiments ± SEM.