TABLE 2.
Kinetic parameters for S. oneidensis outer membrane c-type cytochromes MtrC and OmcA at 25°C
| Complex | Ferric ion/ligand ratio | Second-order reaction rate constants for MtrC (μM−1 s−1)
|
Second-order reaction rate constants for OmcA (μM−1 s−1)
|
||
|---|---|---|---|---|---|
| Fast reaction | Slow reaction | Fast reaction | Slow reaction | ||
| Fe-citrate | 1.5:1 | 0.2752 ± 0.0062 (74)b | 0.0112 ± 0.0003 (26) | 0.0373 ± 0.0088 (30) | 0.0117 ± 0.0008 (70) |
| 10:1 | 0.3362 ± 0.0678 (78) | 0.0113 ± 0.0013 (22) | 0.0429 ± 0.0058 (40) | 0.0111 ± 0.0006 (60) | |
| Avga | 0.3057 ± 0.0545 | 0.0113 ± 0.0008 | 0.0401 ± 0.0073 | 0.0114 ± 0.0007 | |
| Fe-NTA | 1.5:1 | 0.2786 ± 0.0049 (86) | 0.0656 ± 0.0035 (14) | 0.1757 ± 0.0168 (53) | 0.0224 ± 0.0016 (47) |
| 10:1 | 0.2760 ± 0.0269 (100) | NDc | 0.2373 ± 0.0061 (62) | 0.0237 ± 0.0005 (38) | |
| Avga | 0.2773 ± 0.0173 | ND | 0.2065 ± 0.0356 | 0.0231 ± 0.0013 | |
| Fe-EDTA | 1.5:1a | 0.7207 ± 0.1589 (100) | ND | 0.6388 ± 0.0272 (82) | 0.0272 ± 0.0053 (18) |
| 10:1 | 0.8721 ± 0.0698 (100) | ND | 0.6033 ± 0.0328 (86) | 0.0151 ± 0.0061 (14) | |
| Avga | 0.7964 ± 0.1376 | ND | 0.6246 ± 0.0283 | 0.0285 ± 0.0069 | |
a
The data are the statistical averages of rate constants at all three [Fe]/[cytochrome] ratios, 150:5, 200:3.3, and 240:2.
b
The numbers in parentheses are the percentages of measurements for which the ratio of [Fe] to [cytochrome] was 3:1 at an Fe(III) concentration of 1.5 × 10−4 M.
c
ND, not determined.