Table 1.
Interactions of mutant β clamp proteins with Pol IIIα and Pol IV
| β clamp | Pol IIIα* |
Pol IV† |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| KD, nM | ka, M−1s−1 | kd, s−1 | n | χ2 | KD, nM | ka, M−1s−1 | kd, s−1 | n | χ2 | |
| β+ | 108 | 6.75 × 104 | 7.26 × 10−3 | 1 | 4.2 | 465 | 1.53 × 104 | 7.13 × 10−3 | 2 | 10.7 |
| βC | 1,780 | 2.38 × 103 | 4.23 × 10−3 | 1 | 7.3 | 1,290 | 3.77 × 103 | 4.84 × 10−3 | 2 | 10.1 |
| β+/βC | 172 | 7.27 × 104 | 12.5 × 10−3 | 1 | 3.0 | 600 | 4.89 × 103 | 2.94 × 10−3 | 2 | 9.3 |
| βR | 64 | 9.45 × 104 | 6.00 × 10−3 | 1 | 5.4 | 657 | 4.87 × 103 | 3.20 × 10−3 | 2 | 8.7 |
Kinetic constants describing the interaction of β+, βC, and β+/βC with Pol IIIα (14), and β + with Pol IV (40) were reported previously, and are included here for comparison to results observed with other mutant clamp proteins. n refers to the stoichiometry between Pol IIIα or Pol IV and the dimeric clamp, and was calculated under conditions of saturating analyte. χ2 values describe the fit of the raw data to the 1:1 Langmuir model.
*Approximately 100 RU of each clamp protein was captured using BSA free anti·Penta-His antibody (Qiagen) conjugated to a C1 chip (GE Healthcare), followed by injection of 1–1,000 nM Pol IIIα, as described (14).
†Approximately 250 RU of the indicated clamp protein was captured using BSA free anti·Penta-His antibody (Qiagen) conjugated to a CM5 chip (GE Healthcare), followed by injection of 15–1,500 nM Pol IV as described (40).