Table 2 Reactivity of cysteines of native Bcp1 and its mutants toward thiol reagents, pH 7.4.
Reagents | Free Cys | Free GSH | Reduced Bcp1 | Reduced C45S | Reduced C50S | |||
|---|---|---|---|---|---|---|---|---|
k (M−1 s−1) | k (M−1 s−1) | k (M−1 s−1) (-SH/mole Bcp1) | E.R. | k (M−1 s−1) (-SH/mole Bcp1) | E.R. | k (M−1 s−1) (-SH/mole Bcp1) | E.R. | |
GSSG | 0.7a (0.2)b | — | 0.35 ± 0.02 (1) | 0.5 1.7 | — | — | — | — |
Cystine | — | 12 | 115 ± 10 (1) | 9.6 | 4.2 ± 0.4 (0.6) | 0.35 | 3.5 ± 0.2 (0.65) | 0.29 |
Cystamine | — | 55 | 33 ± 3 (1) | 0.6 | 2.1 ± 0.2 (0.6) | 0.04 | 3.5 ± 0.1 (0.65) | 0.06 |
Homocystine | — | 0.6 | 15 ± 1 (1) | 25 | 3.8 ± 0.2 (0.6) | 6.3 | 0.5 ± 0.1 (0.65) | 0.8 |
DTNB | ||||||||
(pH 5.0) | — | 20 | 360 ± 20 (1) | 18 | — | — | — | — |
DTNB (pH 7.4) | — | 5000 | — | — | 1400 ± 200 (0.6) | 0.28 | — | — |
DTNB (pH 6.0) | — | 150 | — | — | — | — | 925 ± 50 (0.65) | 6.2 |
CDNB | — | 0.07 | 0.55 ± 0.03 (1) | 7.8 | 0.18 ± 0.02 (0.6) | 2.6 | 0.39 ± 0.02 (0.65) | 5.6 |
NBD-Cl | — | 8 | 27 ± 3 (1) | 3.4 | 3.4 ± 0.2 (0.6) | 0.4 | 4.9 ± 0.2 (0.65) | 0.6 |
