Table 5. Summary of the suggested roles of individual Cys residues in AtSS1.
N.D. not determined.
| Cys residues | Observed effects for proteins | Possible role of the Cys residue(s) | ||||
|---|---|---|---|---|---|---|
| Reactivation (%) | Vmax | Km, fold change | Redox sensitivity (%) | Protein production | ||
| WT | 85 | 100 | 1.00 | 77 | Normal | N.D. |
| C164S | N.D. | 36 | 1.33 | 80 | N.D. | Catalysis (possibly in acceptor binding). Redox regulatory disulfide with Cys545. Protein folding (intermediate disulfide with Cys265) |
| C209S | 66 | 90 | 1.67 | 99 | N.D. | Protein folding. Alternative partner for Cys545, Cys164 |
| C261S | 70 | 95 | 2.44 | 99 | N.D. | Protein folding |
| C265S | N.D. | 13 | 0.96 | 98 | N.D. | Protein folding. Catalysis (rather indirect influence) |
| C442S | 9.5 | 86 | 1.28 | 99 | N.D. | Protein folding. Critical for stability upon oxidation |
| C458S | 35 | 88 | 1.32 | 99 | N.D. | Protein folding. Important for stability upon oxidation |
| C533S | 44 | 93 | 1.41 | 99 | N.D. | Protein folding. Important for stability upon oxidation |
| C545S | N.D. | 38 | 9.7 | 55 | N.D. | Catalysis (binds glucose to be transferred to the acceptor). Redox regulatory disulfide with Cys164 |
| C164S_C265S | N.D. | 5 | 4.22 | 59 | Very low yield. Truncated protein | Critical for protein folding |
| C164S_C545S | 49 | 28 | 16.0 | 30 | Low yield | Main redox regulatory disulfide |
| C265S_C545S | N.D. | 9 | 11.0 | 69 | Very low yield | Catalysis (combinatorial effect of the two mutations) |