Transthyretin variants with improved inhibition of β-amyloid aggregation.
Aggregation of β-amyloid (Aβ) is widely believed to cause neuronal dysfunction in Alzheimer's disease. Transthyretin (TTR) binds to Aβ and inhibits its aggregation and neurotoxicity. TTR is a homotetrameric protein, with each monomer containing a short α-helix and two anti-parallel β-sheets. Dimers pack into tetramers to form a hydrophobic cavity. Here we report the discovery of a TTR mutant, N98A, that was more effective at inhibiting Aβ aggregation than wild-type (WT) TTR, although N98A and WT bound Aβ equally. The N98A mutation is located on a flexible loop distant from the putative Aβ-binding sites and does not alter secondary and tertiary structures nor prevent correct assembly into tetramers. Under non-physiological conditions, N98A tetramers were kinetically and thermodynamically less stable than WT, suggesting a difference in the tetramer folded structure. In vivo, the lone cysteine in TTR is frequently modified by S-cysteinylation or S-sulfonation. Like the N98A mutation, S-cysteinylation of TTR modestly decreased tetramer stability and increased TTR's effectiveness at inhibiting Aβ aggregation. Collectively, these data indicate that a subtle change in TTR tetramer structure measurably increases TTR's ability to inhibit Aβ aggregation.
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, WI 53706, USA.
Parth
P
Mangrolia
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, WI 53706, USA.
Dennis T
DT
Yang
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, WI 53706, USA.
Regina M
RM
Murphy
D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D001665:Binding Sites; D006801:Humans; D008958:Models, Molecular; D017354:Point Mutation; D011228:Prealbumin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D066263:Protein Aggregation, Pathological / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization
D016229:Amyloid beta-Peptides; D011228:Prealbumin
amyloid; protein aggregation; transthyretin