TABLE 2.
Kinetic parameters for the plasma membrane H+-ATPase AHA2 and C-terminal single, double, and triple mutants and lyso-PC activation measured at 30 °C with 3 mm ATP (n = 3 biological replicates; ±S.E.)
| H+-ATPase variant | Specific activity at 3 mm ATPa | Km(ATP) | Lyso-PC activation, max.b |
|---|---|---|---|
| μmol Pi/mg/min | mm | % | |
| AHA2 | 0.97 ± 0.11 | 1.20 ± 0.10 | 450 ± 2 |
| T947A | 0.62 ± 0.01 | 1.92 ± 0.30 | 612 ± 42 |
| R918A | 0.95 ± 0.07 | 1.48 ± 0.24 | 508 ± 1 |
| L919A | 1.97 ± 0.22 | 0.32 ± 0.08 | 177 ± 1 |
| R920A | 1.22 ± 0.09 | 1.42 ± 0.20 | 418 ± 5 |
| E921A | 1.23 ± 0.05 | 1.40 ± 0.30 | 433 ± 15 |
| L922A | 0.80 ± 0.09 | 1.82 ± 0.20 | 585 ± 45 |
| H923A | 1.21 ± 0.07 | 1.72 ± 0.20 | 469 ± 4 |
| L919A,T947A | 1.38 ± 0.13 | 0.36 ± 0.10 | 192 ± 8 |
| L919A,L922A | 1.71 ± 0.23 | 0.24 ± 0.02 | 182 ± 4 |
| L919A,L922A,T947A | 1.31 ± 0.12 | 0.34 ± 0.06 | 185 ± 8 |
a Specific activity between mutations cannot be compared because expression level may vary.
b Activity at 100% corresponds to the specific activity at 3 mm ATP without lyso-PC.