TABLE 1.
Effects of variants of pyranopterin-coordinating residues on molybdenum reduction potentials and enzyme activity
| Variant | Ema | ΔEmb | E1c | E2d | Kstab | Maximal growth rate | BV−:NO3− activity |
|---|---|---|---|---|---|---|---|
| mV | μm Klett units) h−1 | μmol min−1 mg−1 | |||||
| Wild-type | 142 ± 12 (n = 4) | 0 | 184 ± 10 | 99 ± 16 | 28 | 15.4 ± 0.7 (n = 3) | 48 ± 14 (n = 3) |
| S719A | 146 ± 7 (n = 3) | 4 | 170 ± 19 | 122 ± 7 | 8 | 15.5 ± 1.0 (n = 3) | 54 ± 11 (n = 3) |
| H1163A | 54 ± 3 (n = 4) | −88 | 53 ± 5 | 54 ± 9 | 1 | 6 ± 0.2 (n = 3) | 23 ± 4 (n = 3) |
| H1184A | 106 ± 5 (n = 3) | −36 | 106 ± 14 | 106 ± 5 | 1 | 11.4 ± 0.6 (n = 3) | 36 ± 1 (n = 3) |
| H1092A | −1 ± 3 (n = 3) | −143 | 35 ± 9 | −38 ± 11 | 19 | 4.4 ± 0.5 (n = 2) | 1 ± 0 (n = 3) |
| H1092R | 160 ± 7 (n = 3) | 18 | 225 ± 15 | 95 ± 2 | 171 | 12.8 ± 0.4 (n = 2) | 8.6 ± 1 (n = 3) |
| H1098A | 41 ± 4 (n = 4) | −101 | 139 ± 7 | −57 ± 2 | 1822 | 4.8 ± 0.5 (n = 2) | 16 ± 2 (n = 3) |
a Overall Mo(VI/V/IV) reduction potential at pH 8.0.
b Em (variant) minus Em (wild-type). Where appropriate, p values indicating the statistical significance of each ΔEm are given in the text.
c Mo(VI/V) reduction potential.
d Mo(V/IV) reduction potential.