Table 4.
Self-assembly potentials (Kd(app) values) and factorial decrease of self-assembly potentials (Kd(mut)/Kd(wt)), increase of solubilities, and decrease of amyloidogenicities of mutants in comparison with IAPP
| IAPP and mutantsa | Kd(app) self-assemblyb,c,d,e | Kd(mut)/Kd(wt) (self-assembly)b,c,d,e | -Fold higher solubility than IAPPf | -Fold lower amyloidogenicity than IAPPg |
|---|---|---|---|---|
| nm | ||||
| IAPP | 9.7 ± 0.9d | 1 | 1 | 1 |
| 8A | NB | >1000 | >100 | >100 |
| 4A | NB | >1000 | >100 | >100 |
| A(9–12) | 87.8 ± 4.8 | 9 | <100 | >100 |
| A15,23,26 | 10.4 ± 1.1 | 2 | >100 | >100 |
| A16,23,26 | 22.3 ± 2.3 | 2 | <100 | >100 |
| A15,16,26 | 16.9 ± 5.8 | 2 | <100 | <20 |
| A15,16,23 | 17.8 ± 1.4 | 2 | <100 | <20 |
| A15,16 | 132.7 ± 26.6 | 14 | <100 | 20–99 |
| A23,26 | 108.3 ± 3.8 | 11 | >100 | 20–99 |
| A15,23 | 21.7 ± 11.8 | 2 | 50–99 | 20–99 |
| A16,23 | 5.9 ± 1.6 | 1 | <100 | <20 |
| A15,26 | 21.5 ± 3.5 | 2 | <100 | <20 |
| A16,26 | 19 ± 1 | 2 | <100 | <20 |
| A23 | 24.4 ± 4.8 | 3 | <20 | 20–99 |
| A26 | 32 ± 4 | 3 | <20 | <20 |
| A15 | 21.8 ± 1.8 | 2 | <20 | <20 |
| A16 | 58 ± 8 | 6 | <20 | 20–99 |
a Mutants in boldface type are those with strongly diminished binding affinity to Aβ40(42) (Tables 2 and 3). Boldface values indicate strong or medium effects of mutations on IAPP self-assembly potency, solubility, or amyloidogenicity.
b Determined via titrations of Nα-amino-terminal fluorescein-labeled IAPP mutants (5 nm) with non-labeled mutants (pH 7.4).
c Kd(app) values are from three binding curves; numbers in parentheses are S.D. values from three binding curves except for the value of the Fluos-IAPP–IAPP interaction (see Footnote d).
d Kd(app) ± S.E. from Ref. 20.
e NB, no binding at mutant concentrations ≤5 μm.
f Solubilities (aqueous buffer, pH 7.4) determined via sedimentation assays at 100 μm (Fig. 5A); solubilities of A15,23 and single mutants were determined also at 50 and 20 μm, respectively (supplemental Fig. S5); IAPP is insoluble at 1 μm (Fig. 5A) (20).