Identification of beta-amyloid-binding sites on transthyretin.

ABSTRACT: Transthyretin (TTR) binds to the Alzheimer-related peptide beta-amyloid (A?), and may protect against A?-induced neurotoxicity. In this work, the specific domains on TTR involved with binding to A? were probed. An array was constructed of peptides derived from overlapping sequences from TTR. Strong binding of A? to TIAALLSPYSYS (residues 106-117) was detected, corresponding to strand G on the inner ?-sheet of TTR. A? bound weakly to four contiguous peptides spanning residues 59-83, which includes strand E through the E/F helix and loop. To further pinpoint specific residues on TTR involved with A? binding, nine alanine mutants were generated: I68A, I73A, K76A, L82A, I84A, S85A, L17A, T106A and L110A. A? binding was significantly inhibited only in L82A and L110A, indicating that A? binding to TTR is mediated through these bulky hydrophobic leucines. A? binding to L17A and S85A was significantly higher than to wild-type TTR. Enhancement of binding in L17A is postulated to arise from reduced steric restriction to the interior L110 site, since these two residues are adjacent in the native protein. The S85A mutation caused a reduction in TTR tetramer stability; increased A? binding is postulated to be a direct consequence of the reduced quaternary stability.

SUBMITTER: Du J 

PROVIDER: S-EPMC3530273 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature