Table 3.
Properties of EC MnSOD cysteine variants
| Variant | Free SHa(mol SH/ mol protein) | Thiol Status | Metallation state | Specific Activity (U/mg) | Quaternary Structure | Mn Content | Metal Uptakeh |
|---|---|---|---|---|---|---|---|
| S126C | 0.99 | SH | Apob | - | Monomerf | + | |
| Mnc | 4815±232 (66%)e | Dimerf | 0.89±0.01 | ||||
| S126C | 0.02 | -SS- | Apob | - | Dimerf,g | + | |
| Mnc | 4741±82 (65%)e | Dimerf,g | 0.95±0.04 | ||||
| Y174C | 0.02 | -SS- | Apob | - | Dimerg | + | |
| Mnc | 1123±20 (28%)e | n.d. | 0.99±0.01 | ||||
| S126C/Y174C | 0.07 | 2×(-SS-) | Apob | - | Dimerg | + | |
| Mnc | 103±1 (2%)e | n.d. | 0.20±0.01 | ||||
| Mnd | - | n.d. | 0.05±0.02 | ||||
| E170C | 0.02 | (-SS-) | Apob | - | Dimerg | + | |
| Mnc | 44±2 (0.6%) | n.d. | 0.48±0.005 | ||||
| R72C/D147C-bBm | 0.01 | Apob | - | n.d. | + | ||
| Mnc | 6287±70 (86%) | n.d. | 0.89±0.03 | ||||
| H17C/N190C | 0.02 | (-SS-) | Apob | - | n.d. | + | |
| Mnc | 8267±232(113%) | n.d. | 1.02±0.05 |
a
Based on DTNB assay
b
Before metal uptake experiment.
c
After metal reconstitution.
d
After denaturation/renaturation/reconstitution in presence of Mn2+.
e
Relative to WT MnSOD (7328±216 U/mg)
f
Based on size exclusion chromatography
g
Based on nonreducing SDS-PAGE
h
Evaluated by Co2+ quenching in the fluorimetric metal uptake assay.