TABLE 1.
Catalytic properties and metal content of FeFe proteins isolated from different genetic backgrounds
| Purified FeFe protein | Specific activities | Metal content | ||||||
|---|---|---|---|---|---|---|---|---|
| FeFe protein source | Genes inactivated | V added to the media | Protons (1 atm Ar) | N2 (1 atm) and protons | C2H2 (0.4 atm) | Fe content | V content | |
| nmol | nmol | nmol | nmol C2H4/min/mg | mol Fe/mol | mol V/mol | |||
| H2/min/mg | NH3/min/mg | H2/min/mg | nmol C2H6/min/mg | FeFe protein | FeFe protein | |||
| DJ2241 | nifDK, vnfDGK | – | 773 ± 38 | 171 ± 1 | 435 ± 15 |
196 ± 14 6.0 ± 0.2 |
26 ± 0 a | 0.07 ± 0.00 b |
| DJ2290 | nifDK, vnfDGK, anfO | – | 734 ± 33 | 172 ± 7 | 475 ± 20 |
190 ± 2 6.8 ± 1.3 |
29 ± 0 a | 0.06 ± 0.00 b |
| DJ2241 | nifDK, vnfDGK | 5 μM | 520 ± 13 | 55 ± 4 | 374 ± 6 |
97 ± 5 1.6 ± 0.1 |
28 ± 1 | 1.05 ± 0.03 |
| DJ2290 | nifDK, vnfDGK, anfO | 5 μM | 303 ± 13 | 0 ± 0 | 291 ± 7 |
29 ± 2 0.8 ± 0.1 |
32 ± 0 a | 1.65 ± 0.00 b |
| DJ2381 | nifDK, vnfDGK, vnfEN | 5 μM | 903 ± 34 | 213 ± 10 | 508 ± 32 |
236 ± 6 N.D. |
31 ± 1 | 0.12 ± 0.03 |
| DJ2411 | nifDK, vnfDGK, anfO, vnfE | 5 μM | 934 ± 43 | 201 ± 2 | 465 ± 23 |
195 ± 16 N.D. |
N.D. | N.D. |
| DJ2480 | nifDK, vnfDGK, anfO, vnfEN | 5 μM | 971 ± 33 | 228 ± 3 | 510 ± 20 |
202 ± 21 N.D. |
27 ± 0 a | 0.11 ± 0.00 b |
Notes: FeFe proteins were purified from cells grown in the presence or absence of 5 μM V as indicated. Metal contents were quantified by ICP‐MS. Molar ratios were calculated based on the molecular weight of the FeFe protein α2β2δ2 complex. Data presented are the average from at least three independent determinations.
Abbreviation: N.D., not determined.
a
Standard deviation value <1;
b
Standard deviation value <0.001.