TABLE 2.
The effect of C. reinhardtii plastocyanin multiple charge-change mutations on its interactions with cytochrome f at 10 mM ionic strength and pH 7.0
| No. of complexes per 10,000 trajectories |
k2* ( 108) M−1 s−1
|
% WT control | |
|---|---|---|---|
| R57E | 1115 ± 7 | 33.8 ± 1.0 | 169.2 ± 8 |
| K95E | 931 ± 5 | 28.6 ± 0.8 | 143.2 ± 7 |
| WT | 635 ± 10 | 20.0 ± 0.7 | 100.0 ± 4 |
| D59A + D61A | 290 ± 10 | 9.4 ± 0.6 | 46.9 ± 4 |
| E43A + D44A | 237 ± 2 | 7.7 ± 0.5 | 8.6 ± 3 |
| E43A + D61A | 208 ± 6 | 6.8 ± 0.5 | 33.9 ± 3 |
| D53K | 199 ± 4 | 6.5 ± 0.5 | 32.4 ± 3 |
| D59K + D61K | 101 ± 4 | 3.3 ± 0.4 | 16.6 ± 2 |
| E43A + D44A + D61A | 91 ± 4 | 3.0 ± 0.4 | 14.9 ± 2 |
| E43K + D44K | 73 ± 2 | 2.4 ± 0.3 | 12.0 ± 1 |
| EE-off† | 2.3 ± 0.4 | 0.015 ± 0.013 | 0.075 ± 0.065 |
The second-order rate constants, k2, were calculated from the fraction of trajectories that met the preset reaction criteria. In cyt f-PC interactions a value of 16 Å cutoff for Cu-Fe distance was used (see Methods section).
EE-off value was obtained by turning off the electrostatic fields in the wild-type PC-cyt f interactions. Originally, we carried out five sets of 10,000 trajectories (similar to the mutants) to obtain the EE-off rate value, which resulted in zero successful complexes. Therefore, we conducted five sets of 50,000 trajectories to obtain a nonzero rate value at 16 Å cutoff distance in the absence of electrostatic fields.