Table 2.
Rate constants for the individual reaction steps leading to the formation of the mixed-valence form of M160SeM T. thermophilus CuA.
Reaction Stepa | Rate Constant |
---|---|
A + Cu(II) → Iearly | 7.5±1.1 × 103 mol−1s−1 |
Iearly → I | 0.81±0.18 s−1 |
I + Cu(II) → A(S-S) + 2Cu(I) | 3.0±0.31 × 103 mol−1s−1 |
I + Cu(I) → P | 11.0±3.8 × 106 mol−1s−1 |
A + Cu(I) → I-Cu(I) | indeterminate |
A is the bis-thiol apo protein, A(S-S) is the disulfide bridged apo protein, P is the mixed valence product, Iearly is the red copper intermediate, I is the green copper intermediate, and I-Cu(I) the mononuclear Cu(I) intermediate. I-Cu(I) may react with Cu(I) to form the di-Cu(I) product but no information on this step could be extracted from the data. The rate constant for reaction of A with Cu(I) is also not well defined.