Table 1.
Relative affinities of Sec9 monomers for ternary and binary SNARE complexes
| Sec9-H1 (Q468) | Sec9-H2 (Q622) | Sso1 (Q224) | Snc2 (R52) | log(EC50) Sso1 (1–265) | EC50, μM Sso1 (1–265) | log(EC50) Sso1 (188–265) | EC50, μM Sso1 (188–265) |
|---|---|---|---|---|---|---|---|
| Q | Q | Q | R | −6.55 ± 0.21 | 0.283 | −6.46 ± 0.08 | 0.345 |
| R | Q | Q | R | −5.55 ± 0.07 | 2.853 | −5.74 ± 0.12 | 1.811 |
| Q | R | Q | R | −5.68 ± 0.04 | 2.080 | −5.92 ± 0.08 | 1.209 |
| Q | Q | R | R | −6.22 ± 0.29 | 0.607 | n.d. | n.d. |
| Q | Q | Q | Q | −6.42 ± 0.15 | 0.383 | −6.34 ± 0.12 | 0.316 |
| R | Q | Q | Q | −5.74 ± 0.15 | 1.807 | −6.37 ± 0.16 | 0.426 |
| Q | R | Q | Q | −5.68 ± 0.10 | 2.098 | −6.41 ± 0.20 | 0.383 |
| Q | Q | Q | — | −6.52 ± 0.08 | 0.302 | n.d. | n.d. |
| R | Q | Q | — | −5.81 ± 0.26 | 1.561 | n.d. | n.d. |
| Q | R | Q | — | −5.78 ± 0.09 | 1.675 | n.d. | n.d. |
EC50 values were derived from saturation binding curves as shown in Figure 7 and described in MATERIALS AND METHODS. The last two columns represent assays done with an N-terminally truncated form of Sso1 that lacks the region known to drastically reduce the kinetics of SNARE assembly (Nicholson et al., 1998). The top seven rows represent ternary assays in which all three SNARE proteins are present, and the bottom three rows represent binary assays of association between Sec9 and Sso1. Mutant residues are indicated in bold italic type. n.d., not determined.