TABLE 3.
Semi-static GALA and modified Gaussian analysis of transmembrane orientations of related GWALP23 peptides
The parent GWALP23 sequence is acetyl-GGALWLALALAL12AL14ALALWLAGA-amide. In the noted examples, either residue Leu12 or Leu14 (but not both) was changed to His or Lys or Arg, as indicated, and the other residue remained a leucine.
| Lipid and peptide | pH | GALA fit results |
Modified Gaussian resultsa |
Reference | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| τ0 | ρ0 | Szz | RMSD (kHz) | τ0 | ρ0 | σρ | RMSD (kHz) | |||
| DLPC | ||||||||||
| H+/014 | 2.0–8.2b | 26.7° ± 5c | 253° ± 2 | 0.80 | 0.93 | 29° | 253° | 24° | 0.62 | This work |
| R+14 | —d | 26.7° | 260° | 0.83 | 1.58 | 26° | 260° | 0° | 1.65 | 26 |
| H+/012 | 2.0–8.2b | 23.3° ± 3 | 308° ± 2 | 0.70 | 0.66 | 18° | 305° | 15° | 1.34 | This work |
| L12,14 | — | 21.0° | 305° | 0.71 | 0.7 | 23° | 304° | 33° | 0.7 | 23 |
| DOPC | ||||||||||
| H+14 | 2.0 | 14.0° ± 3 | 246° ± 1 | 0.90 | 1.03 | 19° | 247° | 24° | 1.28 | This work |
| R+14 | —d | 15.0° | 247° | 0.93 | 0.89 | 19° | 246° | 17° | 1.33 | 25 |
| K+14 | 5.2 | 15.3° | 228° | 0.88 | 1.20 | 17° | 227° | 21° | 1.28 | 24 |
| H014 | 6.0 | 10.3° ± 1 | 248° ± 2 | 0.89 | 1.36 | 11° | 249° | 18° | 0.67 | This work |
| K014 | 8.2 | 9.0° | 244° | 0.86 | 0.31 | 10° | 243° | 18° | 0.36 | 24 |
| H012 | 4.0 | 6.0° ± 1 | 338° ± 3 | 0.93 | 0.74 | 10° | 332° | 48° | 0.89 | This work |
| H+12e | 2.0 | 81.0° ± 1 | 296° ± 1 | 0.85 | 0.70 | 81° | 297° | 5° | 0.88 | This worke |
| L12,14 | — | 6.0° | 323° | 0.87 | 0.6 | 9° | 321° | 48° | 0.7 | 23 |
a The modified Gaussian analysis followed Sparks et al. (23), with στ assigned a fixed finite value of 10°. στ and σρ are related to the widths of distributions of helix orientations, effectively indicating the uncertainties in τ0 and ρ0.
b In DLPC, the results with His12 and His14 do not depend on pH.
c Because τ0 and ρ0 are derived values from the GALA fits, we report ± numbers that correspond to those ranges where RMSD < 1.5 kHz.
d The results with -R14+ do not depend on pH (24, 25). For the L12,14 peptide, the pH was not buffered.
e Analysis of -H+12 orientation is based on quadrupolar splittings of labeled Ala7 and Ala9 Cα−deuterons along with labeled CD3 groups of Ala7, Ala9, Ala11, and Ala13. About 70% of the -H+12 population exists in this surface-bound state and the other portion remains transmembrane with multi-state behavior.