Table 1.
Protein region contributions in cysteine pKacalculations
| Protein (fragment)/conformers | Trx pKa (calculated)(experimental pKa = 6.3) | DsbA pKa (calculated)(experimental pKa = 3.4) |
| Native/single | 7.1 | 2.6 |
| 5 Å sphere/single | 9.2 | 3.9 |
| 10 Å sphere/single | 7.2 | 2.5 |
| 15 Å sphere/single | 7.2 | 2.7 |
| 25 Å sphere/single | 7.1 | 2.5 |
| 40 Å sphere/single | 7.1 | 2.5 |
| CxxC/single | 7.9 | 4.2 |
| α-β-pro turn/single | 7.0 | 3.0 |
| Native/multi | — | 4.3 |
| CxxC/multi | — | 5.5 |
| α-β-pro turn/multi | — | 4.3 |
FDPB calculations were made with ɛp = 4 and ɛs = 78.4, at 0.15 M ionic strength. Native protein refers to a monomer from the lert (thioredoxin) or 1a21 (DsbA) coordinate files. Spheres of given radius were centered on the SG atom of the more exposed thiolate. The α-β-pro turn fragments consisted of residues 21 to 50 and 73 to 76 for thioredoxin, and 21 to 50 and 149 to 152 for DsbA. Single conformer refers to the crystal structure, and multiple conformers for DsbA were derived from variations in packing of the PH intervening sequence (not applicable for the single conformer of residues GP in thioredoxin). Experimental pKas from Forman-Kay et al. (1992; trx) and Grauschopf et al. (1995; DsbA).