Table 3. Isothermal titration calorimetry demonstrates that only one molecule of (dT)35 can bind with SSB variants that have two of the four OB folds mutated to block ssDNA binding.
Protein | [NaCl] (mM) | Model | n(1,2) Sites | K(1,2) M−1 | ΔH(1,2) kcal mol−1 |
---|---|---|---|---|---|
wtSSB | 2 | One Site | 0.99 ± 0.01 | ≥1010 | (−65.7 ± 0.1) |
wtSSB | 300 | Two Sites | 1† | ≥1010 | (−60.7 ± 0.5) |
2† | (1.30 ± 0.19) × 108 | (−63.9 ± 0.7) | |||
SSB LD | 2 | One Site | 0.95 ± 0.01 | ≥1010 | (−63.3 ± 0.1) |
SSB LD | 300 | Two Sites | 1† | ≥109 | (−59.6 ± 0.7) |
2† | (2.0 ± 0.5) × 106 | (−43.4 ± 0.4) | |||
SSB LD (αΔW) | 2 | One Site | 0.86 ± 0.01 | ≥1010 | (−56.2 ± 0.2) |
SSB LD (αΔW) | 300 | One Site | 0.93 ± 0.01 | (2.36 ± 0.10) × 108 | (−48.8 ± 0.1) |
SSB LD (αΔW F) | 2 | One Site | 0.83 ± 0.01 | (1.6 ± 0.3) × 109 | (−56.2 ± 0.3) |
SSB LD (αΔW F) | 300 | One Site | 0.85 ± 0.01 | (8.7 ± 0.5) × 107 | (−52.0 ± 0.2) |