Table I. Tim8p–Tim13 complex zinc complex.
| Mol zinc:mol complex | Actual (−Zn)a0:1 | Actual (+Zn)a0:1 | Predictedb1:1 | Predictedb6:1 |
|---|---|---|---|---|
| Zinc (sample/background, ppb)c | 0.792/0.352 | 0.821/0.443 | 7.34 | 44.06 |
| Zinc (μM)d | 0.007 | 0.006 | 1.12 | 6.72 |
| Protein (mg/ml)e | 0.071 | 0.074 | ||
| Protein (μM)d | 1.12 | 1.17 | ||
| Zinc per complex | .098 | .081 | 1 | 6 |
Values represent an average of three independent purifications from cells induced in the absence (−Zn) or presence of 1 mM zinc-acetate (+Zn).
Each twin CX3C motif (six per complex) in the Tim8p–Tim13p complex could potentially coordinate one Zn2+. The predicted levels of zinc are shown (in ppb) for hypothetical Tim8p–Tim13p complexes that bind one Zn2+ per complex or one Zn2+ per monomer (six zinc ions total). Predicted values are based on the same concentration of Tim8p–Tim13p complex (−Zn) used in actual measurements.
The average ICP-determined zinc concentration (ppb) is presented along with the average background level of zinc. Background levels of zinc were determined using buffer blanks from the same purification.
The micromolar concentrations of both protein and zinc were calculated assuming a molecular mass of 65.38 atomic mass units (amu) for zinc and 6.32 × 104 amu for the Tim8p–Tim13p complex.
The protein concentration of each sample was determined by quantitative amino acid analysis.