TABLE 2.
Isothermal titration calorimetry of CAPERα UHM binding ULMs or ULM-containing proteins
Average values and S.D. of two independent experiments. ΔG° was calculated using ΔG° = −RTln(KD−1), and −TΔS° was calculated using ΔG° = ΔH° − TΔS°, T = 303 K. Values for each class of multiple sites in the wild-type SF3b155 domain describe binding of one CAPERα UHM to one of these SF3b155 sites. Representative isotherms are given with c-values in supplemental Fig. 1. Boundaries of SF3b155, -W293, -W338 are residues 190–344; ULM5 is residues 333–342 (KRKSRWDETP); ULM5L is residues 333–355 (KRKSRWDETPASQMGGSTPVLTP).
| ULM ligand | KD | Apparent stoichiometry | ΔG° | ΔH° | −TΔS° |
|---|---|---|---|---|---|
| nm | kcal mol−1 | kcal mol−1 | kcal mol−1 | ||
| SF114–132 | 11,000 ± 700 | 1.0 ± 0.1 | −6.9 ± 0.1 | −11.5 ± 0.2 | 4.6 ± 0.2 |
| U2AF65 ULM | 6,500 ± 1100 | 1.1 ± 0.0 | −7.2 ± 0.1 | −14.5 ± 0.4 | 7.3 ± 0.5 |
| SF3b155, high affinity site | 58 ± 2 | 1.7 ± 0.1 | −10.1 ± 0.1 | −16.3 ± 0.8 | 6.3 ± 0.8 |
| SF3b155 low affinity site | 330 ± 4 | 3.2 ± 0.1 | −9.0 ± 0.1 | 0.5 ± 0.2 | −9.5 ± 0.2 |
| SF3b155-W200 | 2,300 ± 100 | 1.0 ± 0.1 | −7.8 ± 0.1 | −17.4 ± 0.2 | 9.6 ± 0.3 |
| SF3b155-W293 | 68,000 ± 1900 | 1.1 ± 0.2 | −5.8 ± 0.1 | −16.0 ± 0.7 | 10.2 ± 0.8 |
| SF3b155-W338 | 14,000 ± 1800 | 1.0 ± 0.1 | −6.7 ± 0.9 | −15.3 ± 0.1 | 8.6 ± 0.1 |
| SF3b155 ULM5 | 2,400 ± 1 | 0.9 ± 0.1 | −7.8 ± 0.1 | −21.9 ± 1.0 | 12.1 ± 1.0 |
| SF3b155 ULM5L | 2,300 ± 200 | 1.0 ± 0.1 | −7.8 ± 0.1 | −18.0 ± 0.4 | 10.1 ± 0.3 |