Figure 4.

PNPase promotes limited degradation of ssDNA. [γ³²P]-ssDNA₆₀ (1 nM) was incubated with increasing concentrations of PNPase (0.02, 0.04, 0.08, 0.16, 0.33 and 0.66 nM) for 30 min in buffer B containing 1 mM ATP, AMP-PNP or lacking a nucleotide cofactor, and the samples were separated in 15% dPAGE. Sizes of molecular markers (in nt) are indicated (lane 20).