Table 1.
ATPase activities associated with the R. sphaeroides magnesium chelatase subunits
| Assay | Subunits added | % radioactivity
|
ATPase activity, nmol of ATP hydrolyzed per min | ||
|---|---|---|---|---|---|
| AMP | ADP | ATP | |||
| 1 | BchD | 2.3 | 2.4 | 95.3 | 0.021 |
| 2 | BchH | 2.7 | 38.8 | 58.5 | 0.19 |
| 3 | BchI | 9.3 | 10.2 | 80.5 | 0.092 |
| 4 | BchD + BchI | 5.0 | 82.8 | 12.2 | 0.24 |
| 5 | BchD | 1.4 | 1.6 | 97.0 | 0.089 |
| 6 | BchH | 0.7 | 5.2 | 94.1 | 0.18 |
| 7 | BchI | 1.1 | 4.7 | 94.3 | 0.17 |
| 8 | BchD + BchH | 0.7 | 4.6 | 94.7 | 0.12 |
| 9 | BchD + BchI | 1.8 | 46.9 | 51.3 | 14.5 |
| 10 | BchH + BchI | 1.1 | 10.3 | 88.6 | 3.4 |
| 11 | BchD + BchH + BchI | 3.5 | 50.5 | 46.0 | 16.5 |
In assays 1–4, activity was determined in the presence of [8-14C]ATP with no unlabeled ATP added. In assays 5–11, activity was measured in the presence of [8-14C]ATP + 1 mM unlabeled ATP. Protein (μg per assay): BchD, 33; BchH, 210; BchI, 90.