Table 1.
The relationship between the pH-dependence of stability, pI, and the pH of maximum fibril formation for several proteins
| Protein | ΔGmax (pH)i (kcal mole−1) | ΔGpij (kcal mole−1) | pIk | pHmaxl |
| RNase Saa,g | 7.0 (5.0) | 4.0 | 3.5 | 3.1 |
| RNase T1b | 8.8 (4.5) | 8.0 | 3.8 | 3.7 |
| α-synucleinc | NA | NA | 4.7 | 4.0 |
| bsHPrd | 4.5 (7.0) | 3.5 | 4.9 | 4.8 |
| TTRe | NA | NA | 5.2 | 4.4 |
| RNase Sa2a | 4.7 (4.5) | 4.2 | 5.3 | 5.8 |
| Aβ peptidef | — | — | 5.3 | 5.3 |
| ecHPrd | 4.5 (7.0) | 3.5 | 5.4 | 5.4 |
| RNase Sa 3Kg | 5.5 (5.0) | 4.2 | 6.4 | 6.4 |
| RNase Sa3a | 8.9 (5.5) | 4.0 | 7.2 | 7.4 |
| RNase Ab | 9.2 (7.0) | 9.0 | 9.6 | 8.9 |
| RNase Sa 5Kg | 5.5 (5.0) | 2.0 | 10.2 | >10 |
| HEWLh | NA | NA | 11.2 | >10 |
a Stability and pI values are from Pace et al. (1998) and the pH of maximum fibril formation was determined as described in the text.
b Stability and pI values are from Pace et al. (1990) and the pH of maximum fibril formation was determined as described in the text.
c The pI was calculated as described in Shaw et al. (2001), and the pH of maximum fibril formation is from Hoyer et al. (2002). There are no entries for stability, because this is not a globular protein.
d Unpublished results from this laboratory (J.P.S. and J.M.S.).
e The pI was calculated as described in Shaw et al. (2001), and pH of maximum fibril formation is from Jiang et al. (2001).
f The pI and pH of maximum amyloid formation are from Wood et al. (1996).
g Stability and pI values are from Shaw et al. (2001), and the pH of maximum fibril formation are from Figure 3 ▶.
h Stability and pI are from Pfeil and Privalov (1976), and the pH of maximum stability was determined as described in the text.
i ΔGmax (pH) is the maximum conformational stability, which occurs at the indicated pH, expressed in kcal mole−1.
j ΔGpI is the conformational stability at pH = pI for the indicated protein, expressed in kcal mole−1.
k The pI value for the indicated protein, either measured or calculated as indicated.
l pHmax is the pH where fibril formation is maximal, based on the ThT assay described in the text.