TABLE 4.
Solubilization of iron(III) reductase from membrane fractions of G. sulfurreducens
| Fraction | Protein (mg) | Iron(III)
reductase activitya with:
|
|||||
|---|---|---|---|---|---|---|---|
| NADH
|
Horse heart cytochrome c
|
||||||
| Sp act (mU/mg of protein) | Total activity (mU) | % | Sp act (mU/mg of protein) | Total activity (mU) | % | ||
| Membrane fraction before extraction | 6.0 ± 1.0 | 6.0 ± 1.0 | 36.0 ± 6.0 | 100 | 4.0 ± 0.5 | 24.0 ± 3.0 | 100 |
| Soluble fraction after extraction | 3.6 ± 0.2 | 1.43 ± 0.2 | 5.1 ± 0.6 | 14 | 12.5 ± 1.0 | 45.2 ± 5.0 | 188 |
| Membrane fraction after extraction | 2.1 ± 0.3 | 4.5 ± 0.5 | 9.5 ± 1.0 | 27 | 7.9 ± 1.0 | 17.0 ± 2.0 | 71 |
a
Reactions were performed in 50 mM HEPES buffer (pH 7) containing 0.3 mM Fe(III)-NTA, 0.5 mM ferrozine, and either 1 mM NADH or 4 μM horse heart cytochrome c. An activity of 1 mU corresponds to 1 nmol of Fe(II) formed per min.