Table 3.
Thermodynamic parameters for peptide binding to CaM proteins as determined by ITC
| Protein | Conditions∗ | N | Ka (M−1) | ΔH (kJ/mol) | TΔS (kJ/mol) | ΔCp (kJ/mol•K) |
|---|---|---|---|---|---|---|
| smMLCKp peptide | ||||||
| Ca2+-wt-CaM | 25.0°C | 0.8 ± 0.0 | 6.7 ± 0.2 × 107 | −88.9 ± 0.1 | −44.2 | |
| Ca2+-wt-CaM | 17.6°C | 0.9 ± 0.0 | 1.3 ± 0.3 × 107 | −59.7 ± 0.7 | −20.0 | −3.6 |
| Ca2+-wt-CaM | 10.1°C | 0.8 ± 0.0 | 4.6 ± 1.1 × 107 | −35.8 ± 0.3 | 5.8 | |
| Ca2+-SeMet-CaM | 25.0°C | 0.8 ± 0.0 | 9.7 ± 0.6 × 107 | −92.4 ± 0.2 | −46.7 | |
| Ca2+-SeMet-CaM | 17.6°C | 0.8 ± 0.0 | 1.3 ± 0.2 × 107 | −66.8 ± 0.9 | −27.3 | −3.4 |
| Ca2+-SeMet-CaM | 10.2°C | 0.8 ± 0.0 | 2.5 ± 0.4 × 107 | −41.2 ± 0.3 | −1.1 | |
| Ca2+-Eth-CaM | 25.0°C | −74.3 ± 2.2 | ||||
| Ca2+-Eth-CaM | 17.6°C | −49.1 ± 0.7 | −3.4 | |||
| Ca2+-Eth-CaM | 10.2°C | −23.8 ± 0.3 | ||||
| Ca2+-Nle-CaM† | 25.0°C | 0.9 ± 0.1 | 3.6 ± 2.6 × 107 | −90.4 ± 3.7 | −47.8 ± 3.3 | |
| Ca2+-Nle-CaM | 17.6°C | 1.0 ± 0.0 | 2.5 ± 0.5 × 107 | −57.5 ± 0.5 | −16.3 | −3.9 |
| Ca2+-Nle-CaM | 10.2°C | 0.9 ± 0.0 | 2.0 ± 1.2 × 108 | −33.2 ± 0.3 | 11.9 | |
| Ca2+-CT-CaM | 25.0°C | 0.9 ± 0.0 | 8.4 ± 0.7 × 107 | −77.2 ± 0.2 | −32.0 | |
| Ca2+-CT-CaM | 17.6°C | 1.0 ± 0.0 | 2.3 ± 0.9 × 107 | −43.7 ± 0.9 | −2.7 | −3.8 |
| Ca2+-CT-CaM | 10.2°C | 1.0 ± 0.0 | 2.4 ± 0.9 × 108 | −20.6 ± 0.1 | 24.8 | |
| Ca2+-SeMet-CT-CaM | 25.0°C | 0.8 ± 0.0 | 1.9 ± 0.2 × 107 | −76.8 ± 0.5 | −35.2 | |
| Ca2+-SeMet-CT-CaM | 17.6°C | 0.9 ± 0.0 | 1.1 ± 0.2 × 107 | −44.5 ± 0.7 | −5.2 | −3.7 |
| Ca2+-SeMet-CT-CaM | 10.2°C | 0.9 ± 0.0 | 1.9 ± 1.0 × 107 | −21.5 ± 0.7 | 18.1 | |
| NtMKP1b peptide | ||||||
| apo-wt-CaM | 0 mM KCl | 1.0 ± 0.0 | 8.0 ± 0.3 × 105 | −42.3 ± 0.2 | −8.6 | |
| apo-wt-CaM | 100 mM KCl | 0.9 ± 0.2 | 1.9 ± 0.3 × 104 | −32.4 ± 7.5 | −8.0 | |
| apo-SeMet-CaM | 0 mM KCl | 1.0 ± 0.0 | 1.5 ± 0.1 × 106 | −29.7 ± 0.1 | 5.6 | |
| apo-Eth-CaM | 0 mM KCl | 0.9 ± 0.0 | 1.5 ± 0.1 × 106 | −43.6 ± 0.3 | −8.3 | |
| apo-Nle-CaM | 0 mM KCl | 1.1 ± 0.0 | 6.1 ± 0.8 × 105 | −12.0 ± 0.2 | 21.1 | |
| apo-CT-CaM† | 0 mM KCl | 1.1 ± 0.0 | 6.2 ± 0.8 × 105 | −15.7 ± 0.6 | 17.4 ± 0.9 | |
| apo-CT-CaM | 100 mM KCl | 0.8 ± 0.2 | 4.3 ± 1.9 × 104 | −7.0 ± 2.9 | 19.5 | |
| apo-SeMet-CT-CaM | 0 mM KCl | 0.9 ± 0.0 | 4.5 ± 0.3 × 105 | −14.9 ± 0.2 | 17.5 | |
∗
All smMLCKp peptide experiments were performed in 100 mM KCl, and all NtMKP1b peptide experiments were performed at 25°C.
†
Value represents the average and SD of three independent measurements. All other error estimates are derived from curve-fitting uncertainties.