Table 5.
Binding energies for PSBD mutants relative to wild type, in complex with E3 dimer, and estimated entropic contributions
| Experiment (kJ/mole) | Calculation (kJ/mole) | ||||||
| ΔΔG0 | ΔΔH0 | Δ(TΔS0) | Δ(TΔS)QWAT | Δ(TΔS)SC | Δ(TΔS)NP | Δ{Δ(TΔS)} | |
| R135A | −11.7 | +20.1 | +31.8 | +20.8 | −1.0 | −0.3 | +19.5 |
| R139A | −10.5 | −10.5 | 0.0 | +12.1 | −3.5 | −6.0 | +2.6 |
Experimental data from Jung et al. (2002), differenced for wild type-mutant values. Calculations differenced for complexation, TΔS = TScomplex - [TSE3dimer + TSPSBD], followed by wild type to mutant differencing giving Δ(TΔS). Charge hydration entropy Δ(TΔS)QWAT derived from fraction of first hydration shell that is buried at interface for ionizable groups, multiplied by the cysteine shell value frompKa fitting of 36 kJ/mole. Side chain entropy Δ(TΔS)SC taken from mean-field calculations (Koehl and Delarue 1994; Cole and Warwicker 2002). Entropy changes associated with nonpolar surface burial Δ(TΔS)NP were approximated with the multiplicative factor 0.1 kJ/mole/Å2.