FIG. 1.

Recombinant tCid1 is both a strong PAP and PUP. (A) After induction with IPTG, glutathione S-transferase-tagged tCid1 was isolated from E. coli BL21(DE3) pLysS cells with glutathione-Sepharose. tCid1 was released from the glutathione-Sepharose by cleavage with 3C protease. (B) tCid1 was incubated with a 5′-labeled (A)₁₅ primer and 0.5 mM of either ATP, CTP, GTP, or UTP for 30 min at 37°C (A, C, G, or U, respectively). Reaction products were then separated by 12% urea-polyacrylamide gel electrophoresis. As a negative control, (A)₁₅ was incubated with ATP but without tCid1 (No Protein). (C to F) Densitometry plots of the ATP, CTP, GTP, and UTP lanes in panel B.