Figure 8.
Single-turnover kinetics of DNA unwinding for 50-nt-tailed ss/dsDNA substrates of different duplex lengths. A 5 nM 50-nt-3′-tailed ss/dsDNA substrate was first pre-incubated with 200 nM PcrA helicase for 5 min, the reaction was then initiated by rapid addition of 1 mM ATP and excessive protein trap (dT56, 2 μM). The lines represented the best fits of the data to Equation (3) with n = 2, 3, 4; A=0.053 ± 0.001, 0.232 ± 0.002, 0.119 ± 0.001; kobs=6.9 ± 0.2, 9.2 ± 0.1, 8.4 ± 0.1 s−1 for the 12-, 16-, and 20-bp duplex substrates, respectively.