FIG 3.

Clamp activity of the HIV-1 RT mutants. Equal DDDP activities of the indicated HIV-1 RT versions were assayed for the clamp assay, using the two methods described here (see Materials and Methods; see also panel C. (A) Clamp gel assay. S, 2- nt substrate; P, 59-nt products. (B) ELISA-based clamp method. Data are represented as means ± the standard deviations (SD). ***, P < 0.001 (as determined by paired two-tailed t test). (C) Nucleic acid clamp scheme. 1, Primer (P) annealed to template (T1) with 2-nt overhang in its 3′ end was incubated with a second template. This second template (T2) has 2 nt complementarily between their 3′ ends. Then, HIV-1 RT was added to the mixture along with all dNTPs. 2, HIV-1 RT clamps the 2 nt complementarily at the 3′ end of P and the 5′ end of T2. 3, T2 serves as the template for DNA elongation of the clamped primer. This scheme was prepared according to our previous publications (6, 7).