The importance of a gatekeeper residue on the aggregation of transthyretin
Background: Proteins have adopted negative design to diminish aggregation. Results: The replacement of Lys-35 by Leu increases the amyloidogenicity of the 26-57 segment of TTR as well as the entire protein. Conclusion: Lys-35 is as a gatekeeper residue in TTR, and its protective effect is suppressed...
| Autores: | , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2014 |
| País: | España |
| Institución: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglés |
| OAI Identifier: | oai:ddd.uab.cat:185077 |
| Acceso en línea: | https://ddd.uab.cat/record/185077 https://dx.doi.org/urn:doi:10.1074/jbc.M114.563981 |
| Access Level: | acceso abierto |
| Palabra clave: | Amyloid Heparin Peptides Protein Aggregation Protein Misfolding Aggregation Propensity Gatekeeper Residue Rational Mutation Transthyretin |
| Sumario: | Background: Proteins have adopted negative design to diminish aggregation. Results: The replacement of Lys-35 by Leu increases the amyloidogenicity of the 26-57 segment of TTR as well as the entire protein. Conclusion: Lys-35 is as a gatekeeper residue in TTR, and its protective effect is suppressed by heparin. Significance: The elucidation of the principles that govern protein aggregation is helpful for the design of strategies against amyloid diseases. Protein aggregation into β-sheet-enriched amyloid fibrils is associated with an increasing number of human disorders. The adoption of such amyloid conformations seems to constitute a generic property of polypeptide chains. Therefore, during evolution, proteins have adopted negative design strategies to diminish their intrinsic propensity to aggregate, including enrichment of gatekeeper charged residues at the flanks of hydrophobic aggregation-prone segments. Wild type transthyretin (TTR) is responsible for senile systemic amyloidosis, and more than 100 mutations in the TTR gene are involved in familial amyloid polyneuropathy. The TTR 26-57 segment bears many of these aggressive amyloidogenic mutations as well as the binding site for heparin. We demonstrate here that Lys-35 acts as a gatekeeper residue in TTR, strongly decreasing its amyloidogenic potential. This protective effect is sequence-specific because Lys-48 does not affect TTR aggregation. Lys-35 is part of the TTR basic heparin-binding motif. This glycosaminoglycan blocks the protective effect of Lys-35, probably by neutralization of its side chain positive charge. A K35L mutation emulates this effect and results in the rapid self-assembly of the TTR 26-57 region into amyloid fibrils. This mutation does not affect the tetrameric protein stability, but it strongly increases its aggregation propensity. Overall, we illustrate how TTR is yet another amyloidogenic protein exploiting negative design to prevent its massive aggregation, and we show how blockage of conserved protective features by endogenous factors or mutations might result in increased disease susceptibility. |
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