Table 1.
Range of cytochrome bo3 enzyme activity in wild-type (wt) and mutant E. coli membranes (m) and isolated enzyme (i), and proton translocation efficiency in cells
| Strain (Cyt bo3 numbering) | Enzyme location | Activity, % of wt | H+/e− |
|---|---|---|---|
| Wild type | m, i | 100 | 1.6–2.2 |
| R481Q | m | 70–80 | 1.6–2.0 |
| i | 54–64 | ||
| R481M | i | 2–8 | — |
| R481N | i | 51–65 | 1.0–1.3 |
| R481L | i | 35–45 | 1.0–1.3 |
| R482Q | m | 75–95 | 1.7–2.1 |
| i | 46–60 | ||
| R482N | m | 48–58 | 1.7–2.2 |
| i | 33–39 | ||
| R482L | m | 75–85 | 1.7–2.0 |
| R481Q/R482Q | i | 35–45 | 0.9–1.2 |
Wild-type activity range: 400–750 (m) and 350–560 (i) electrons per sec per bo3. Methods for determining proton translocation and enzyme activity and for mutagenesis are described in refs. 7, 8, and 14. In the quinol oxidase cytochrome bo3 1 H+/e− is released to the outside of the cells due to the oxidation of hydroquinone.