Table 2.
Inhibition of KcsA-Shaker by Hui1 variants
| Toxin | Ki, nM | Variant/Hui |
| Hui1 | 0.50 ± 0.03 | =1 |
| Hui1-Arg0 | 0.7 ± 0.1 | 1.4 |
| Hui1-Lys3Ile | 0.9 ± 0.1 | 1.8 |
| Hui1-Glu10Arg | 4.1 ± 0.4 | 8.2 |
| Hui1-Arg15Gln | 2.6 ± 0.5 | 5.2 |
| Hui1-Ser19Ala | 46 ± 3.5 | 92 |
| Hui1-Lys21Asn | 20 ± 2.0 | 40 |
| Hui1-Tyr22Ala | 4,260 ± 860 | 8,520 |
| Hui1-Arg23Ala | 0.25 ± 0.05 | 0.5 |
| Hui1-Arg23Lys | 0.45 ± 0.03 | 0.9 |
| Hui1-Lys28Ala | 0.40 ± 0.14 | 0.8 |
Equilibrium inhibition constants (Ki ± SEM) were determined by two-electrode voltage clamp as described in Fig. 3 (n = 5–12 oocytes). To test the influence of nonconservative differences between Hui1 and ShK on blockade, Hui1 toxins were produced with an added Arg0 or the changes Lys3Ile, Glu10Arg, or Arg15Gln. Hui1 residues Ser19, Lys21, Tyr22, and Arg23 were studied based on the importance of analogous residues in other SAK1 toxins.