Figure 3.

PcrA has bipolar 3′→5′ and 5′→3′ helicase activities. ³²P-labeled substrates were incubated with the indicated amounts of PcrA, and the products resolved by native PAGE. The probes used are listed in Table 1 and their structures are depicted in Figure 1. ds, substrates containing partial or fully duplex DNA; ss, single-stranded DNA.