Table 3.
Factorial decrease of apparent binding affinity (Kd(mut)/Kd(wt)) of mutants to IAPP, Aβ40, and Aβ42 as compared with wild-type IAPP
Apparent Kd values determined by fluorescence spectroscopic titrations (Table 2): Nα-terminal fluorescein-labeled IAPP mutants (5 nm) were titrated with IAPP, Aβ40, or Aβ42 (pH 7.4). Mutants/values in boldface type indicate ≥19-fold weaker binding than IAPP.
| IAPP and mutants | Kd(mut)/Kd(wt) (with IAPP) | Kd(mut)/Kd(wt) (with Aβ40) | Kd(mut)/Kd(wt) (with Aβ42) |
|---|---|---|---|
| IAPP | 1 | 1 | 1 |
| 8A | 850 | >200a | >45a |
| 4A | 450 | >200a | >45a |
| A(9–12) | 3 | 10 | 1 |
| A15,23,26 | 1 | 4 | 1 |
| A16,23,26 | 1 | 3 | 1 |
| A15,16,26 | 6 | 6 | 2 |
| A15,16,23 | 2 | 4 | 0.5 |
| A15,16 | 1 | 8 | 0.5 |
| A23,26 | 5 | 19 | 1 |
| A15,23 | 2 | >200a | >45a |
| A16,23 | 2 | 4 | 1 |
| A15,26 | 2 | 8 | 3 |
| A16,26 | 2 | 2 | 1 |
| A23 | 6 | >200a | 1 |
| A26 | 5 | 44 | 1 |
| A15 | 1 | 8 | 2 |
| A16 | 4 | 4 | 2 |
a No binding at ≤5 μm.