Table 2.
Inhibitory effect of HDQ on the quinol cytochrome c reductase of WT and mutant mitochondria
| Cytochrome b WT and mutation(s) | Turnover no.a (s−1) | IC50/bc1 complexb |
||
|---|---|---|---|---|
| HDQ | Antimycin | Azoxystrobin | ||
| WT | 33 | 4 | 0.5 | 5 |
| Qi site | ||||
| G33A | 20 | 30 | 0.4 | ND |
| G37S | 20 | 4 | 0.4 | ND |
| K228M | 16 | 30–50 | 0.8 | 4 |
| Qo site | ||||
| G143A | 15 | 4 | 0.5 | >20 |
| Qi and Qo | ||||
| G143A+K228M | 18 | 30–40 | 0.9 | >20 |
a
The turnover number is the amount of cytochrome c reduced per bc1 complex per s using 40 μM decylubiquinol (see Materials and Methods). The measurements were repeated at least twice. The errors did not exceed 10% of the presented values.
b
Values are presented as the ratio of the IC50 to the concentration of the monomeric bc1 complex (estimated using the cytochrome optical signal as described in Materials and Methods). For example, 0.5 molecules of the tight binding inhibitor antimycin were added per monomeric bc1 complex to inhibit the quinol cytochrome c reductase activity by 50%. ND, not determined.