TABLE 1.
α-Helical content and thermodynamic parameters of WT and elongation variants of lipid-free apoA-I determined by far-UV CD
| apoA-I | α-Helix (%)a | Number of Residues | Tm (°C)c | ΔHv (kcal/mol)c | ΔGD0 (kcal/mol)d | |
| In Protein | In Helixb | |||||
| Δ(185-243) | 68 ± 2e | 185 (−59) | 125 (−7) | 58 ± 1e | 40 ± 4e | 6.2 ± 0.5e |
| Δ(198-243) | 63 ± 1e | 198 (−46) | 125 (−7) | 63 ± 1e | 36 ± 2e | 6.1 ± 1.0 |
| Δ(209-243) | 60 ± 2e | 209 (−35) | 125 (−7) | 63 ± 1e | 35 ± 3e | 5.4 ± 1.0 |
| Δ(220-243) | 57 ± 1e | 220 (−24) | 125 (−7) | 62 ± 1e | 35 ± 3e | 5.1 ± 1.0 |
| Δ(231-243) | 54 ± 1 | 231 (−13) | 125 (−7) | 62 ± 1e | 30 ± 1e | 5.1 ± 0.3 |
| WT | 54 ± 1 | 244 | 132 | 64 ± 1 | 22 ± 2 | 4.6 ± 0.3 |
Values are the average ± SD from three to nine experiments for three independent preparations of each protein.
Estimated from the value [Θ222] at pH 7.4 and 25°C.
The number of residues in the helical conformation was estimated by multiplying the number of residues in the protein by its α-helical content. Values in parentheses show change in the number of residues compared with WT.
Parameters determined from the thermal unfolding curves. Tm is the maximum of the first derivative d(Θ222)/dT; the effective enthalpy, ΔHv, were determined from van’t Hoff analysis of the thermal unfolding curves.
The conformational stability, ΔGD0, was determined by the linear extrapolation method from the GdnHCl induced unfolding curves.
Significance of difference from the value for WT: P < 0.05.