TABLE 3.
Variant ApbC proteins bind and transfer iron-sulfur clusters
ApbC proteins were reconstituted as described under “Experimental Procedures.” Iron and sulfide were quantified as described elsewhere (39). Metal binding data are the average of two independent reconstitutions.
| ApbC variant | Iron | Sulfur | Rate of cluster transfer to Leu-1a |
|---|---|---|---|
| m-1 min-1 | |||
| ApbC | 2.2 ± 0.2 | 2.1 ± 0.1 | 39,000 ± 2,000 |
| ApbCK16A | 2.0 ± 0.2 | 1.9 ± 0.0 | 25,000 ± 1,000 |
| ApbCK21A | 1.9 ± 0.1 | 1.9 ± 0.1 | 27,000 ± 1,000 |
| ApbCS22A | 1.9 ± 0.2 | 1.8 ± 0.1 | 43,000 ± 1,000 |
| ApbCS182A | 1.7 ± 0.2 | 1.8 ± 0.0 | 45,000 ± 1,000 |
| ApbCC283A | 1.8 ± 0.1 | 1.7 ± 0.2 | 45,000 ± 1,000 |
| ApbCC286A | 1.7 ± 0.2 | 1.9 ± 0.1 | 44,000 ± 5,000 |
| ApbCC283A,C286A | 0.9 ± 0.2 | 1.0 ± 0.0 | NDb |
a
Leu-1 activation assays were conducted as described previously (34). The second-order rate constant of cluster transfer was determined by a linear transformation of the data and fitting the data using linear regression as described under “Experimental Procedures.”
b
ND means not determined.