Table 2.
[3H]S-mTFD-MPPB photoincorporation efficiencies at amino acids within Torpedo nAChR M2 helices that line the ion channel (cpm/pmol of PTH-derivative)
The photolabeling efficiency (cpm/pmol of PTH derivative) for each residue was calculated from the observed 3H release, the initial peptide mass, and repetitive yield as described under “Experimental procedures.” n, the number of samples sequenced. For n = 2, the average efficiencies ± S.D. are tabulated.
| Residues | Photolabeling efficiency |
||||
|---|---|---|---|---|---|
| M2-5′ | M2-6′ | M2-9′ | M2-13′ | M2-/17′ | |
| cpm/pmol | |||||
| α (n = 1) | |||||
| Control | 1 | 3.3 | 16 | 1.4 | <1 |
| Carb | 19 | 51 | 21 | 10 | 13 |
| Carb/PCP | 1.5 | 1.8 | 9 | 18 | 10 |
| β | |||||
| Control (n = 1) | 0.6 | 2 | 6 | 1 | <1 |
| Carb (n = 2) | 1.3 ± 0.6 | 15 ± 1 | 21 ± 11 | 4.5 ± 1.8 | 5.8 ± 2.6 |
| Carb/PCP (n = 2) | 0.3 ± 0.2 | 0.6 ± 0.2 | 4.2 ± 0.3 | 9 ± 4 | 4.2 ± 0.2 |
| γ (n = 2) | |||||
| Control | <1 | 4 ± 1 | 4 ± 1 | 3 ± 1 | 2 ± 1 |
| Carb | 2 ± 1 | 34 ± 6 | 20 ± 13 | 4 ± 1 | 6 ± 2 |
| Carb/PCP | 5 ± 4 | 5 ± 4 | 10 ± 5 | 5 ± 3 | 5 ± 3 |
| δ (n = 2) | |||||
| Control | 0.2 ± 0.1 | 0.4 ± 0.1 | 2.7 ± 0.3 | 0.20 ± 0.05 | 0.21 ± 0.03 |
| Carb | 0.2 ± 0.1 | 2.9 ± 0.4 | 27 ± 2 | 5.2 ± 0.5 | 4.1 ± 0.6 |
| Carb/PCP | <0.1 | 0.30 ± 0.05 | 9.3 ± 1.0 | 5.6 ± 0.5 | 1.7 ± 0.1 |