Table 1.
Activation of Ypt1p by TRAPPI and TRAPPI mutants
| Construct | color in Figure 4D | [TRAPPI] (μM) | k−GDP,obs(s−1)1 | Relative rate increase2 | “kcat/KM” 3 (μM−1 s−1) | Growth Phenotype4 |
|---|---|---|---|---|---|---|
| no TRAPPI | 0 | 1.21 ×10−4 ± 0.22 ×10−4 | 1 | N. A. | N. A. | |
| TRAPPI, wt | 3.5 | >0.07 | >400 | 0.016 ± 0.001 | + | |
| TRAPPI Bet3p (E192A/D193A) | Green | 10 | >0.03 | >400 | 0.003 ± 0.001 | N.A. |
| TRAPPI Bet3p truncation (1–185 only) | 18 | 7.43 ×10−4 ± 0.98 ×10−4 | 6 | < 0.0001 | + | |
| TRAPPI Bet3p truncation (1–188 only) | 24 | 7.03 ×10−4 ± 1.93 ×10−4 | 6 | < 0.0001 | + | |
| TRAPPI Bet3p truncation (1–191 only) | 15 | 1.22 × 10−3 ± 0.19 ×10−4 | 10 | < 0.0001 | N.A. | |
| TRAPPI Bet5p (G46W/S50K) | Cyan | 28 | 1.14 ×10−4 ± 0.33 ×10−4 | 1 | < 0.0001 | - |
| TRAPPI Trs23p (H41A/G42M/A45W/I46R) | Indigo | 30 | 2.03 ×10−4 ± 0.29 ×10−4 | 2 | < 0.0001 | + |
| TRAPPI Trs23p (M200A/P201W/R203S) | purple | 26 | 1.30 ×10−4 ± 0.24 ×10−4 | 1 | < 0.0001 | - |
| TRAPPI Trs23p (S38R) | Yellow | 35 | 1.16 ×10−4 ± 0.084 ×10−4 | 1 | < 0.0001 | - |
| TRAPPI Trs23p (S12K/G14M/L34K) | orange | 28 | 7.2 ×10−5 ± 9.6×10−6 | 1 | < 0.0001 | - |
1
observed GDP dissociation rate constant
2
Relative to Ypt1p in the absence of TRAPPI
3
Catalytic efficiency, taken as initial slope of TRAPPI concentration dependence on exchange rate k−GDP,obs at subsaturating TRAPPI concentration (see Delprato et al., 2004).
4
+/− indicates viability/inviability; “N.A.” means “not available/applicable”.