Table 2.

Gel shifts, SDS binding, helicity, and column MW of TM3/4 hairpins

Hairpin*Gel shift (dMW, %)Bound SDS (g/g)Helicity (MRE X 103)Column MW (mut-wt, %)
V232Dcf-11 ± 2.63.4 ± 0.9−17 ± 1.2+19 ± 1.5
V232K-10 ± 3.03.8 ± 0.6−16 ± 1.1+5.6 ± 1.6
A204L−2.2 ± 2.36.0 ± 0.7−18 ± 1.3+3.4 ± 1.6
P205A/V232Dcf+0.12 ± 5.24.7 ± 0.4−19 ± 2.6+21 ± 0.6
WT+0.42 ± 4.55.4 ± 1.4−18 ± 2.20.0 ± 0.79
V232A+3.6 ± 3.75.2 ± 0.4−18 ± 0.9+6.1 ± 1.9
P205Scf+4.7 ± 6.04.7 ± 1.0−18 ± 0.7+4.4 ± 1.6
Q220W+6.3 ± 2.45.0 ± 0.7-21 ± 2.7-4.9 ± 1.3
G228L+14 ± 5.16.9 ± 1.4-23 ± 1.7+14 ± 2.6
E217V+28 ± 1.36.7 ± 1.0-25 ± 1.7+32 ± 4.0
E217F+29 ± 2.89.4 ± 1.9-28 ± 2.6+17 ± 1.1
E217S/S222E+29 ± 7.610 ± 2.3-25 ± 2.8+35 ± 0.9
Glycophorin§-3.4 ± 0.69.5 ± 1.2+83 ± 5.1
  • *Mutant hairpins are listed in order of increasing gel shift. The mean ± standard deviation of 3–6 independent experiments is shown. Values in each column that significantly differ from WT (P ≤ 0.05 in unpaired 2-tailed t tests) are underlined. The cf superscript denotes substitutions linked to cystic fibrosis in the CF mutation database (http://www.genet.sickkids.on.ca/cftr).

  • Helicity approximated as mean residue ellipticity (MRE) at 222 nm, in units of deg cm2 dmol−1.

  • Change in apparent vs. formula MW estimated from SEC-HPLC retention times (column dMW), normalized to the WT value. Positive values indicate increased hydrodynamic radii vs. WT and vice-versa. The column dMW of the WT TM3/4 hairpin was measured as −29 ± 0.56 %.

  • §Detergent loading, helicity, and column dMW of human glycophorin.