Figure 5.

The χ subunit of γ complex is required for SSB-mediated inhibition of clamp loading on unphosphorylated 5′DNA, but is dispensable in the presence of a 5′P. Reactions were performed as outlined in Figure 1B. DNA structures used are those outlined in Figure 1C: 3′DNA (dark blue), 5′DNA (green), 3′DNA·SSB (light blue) and 5′DNA·SSB (black). Calculated observed rates for β-AF488₂ closing using all DNA structures both with and without the 5′P are reported in Table 3. (A) Representative time courses for β-AF488₂ closing with χ-less γ complex (γ₃δδ′ψ) on phosphorylated DNA. (B) Representative time courses for β-AF488₂ closing with χ-less γ complex on unphosphorylated DNA.