Aprotinin binding to amyloid fibrils

Citation
I. Cardoso et al., Aprotinin binding to amyloid fibrils, EUR J BIOCH, 267(8), 2000, pp. 2307-2311
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
EUROPEAN JOURNAL OF BIOCHEMISTRY
ISSN journal
0014-2956 → ACNP
Volume
267
Issue
8
Year of publication
2000
Pages
2307 - 2311
Database
ISI
SICI code
0014-2956(200004)267:8<2307:ABTAF>2.0.ZU;2-5
Abstract
Different low molecular mass ligands have been used to identify amyloid dep osits. Among these markers, the dyes Thioflavin T and Congo Red interact sp ecifically with the beta-sheet structure arranged in a cross-beta conformat ion, which is characteristic of amyloid. However, the molecular details of this interaction remain unknown. When labelled with technetium-99m, the pro teinase inhibitor aprotinin has been shown to represent a very important ra diopharmaceutical agent for in vivo imaging of extra-abdominal deposition o f amyloid in amyloidosis of the immunoglobulin type. However, no informatio n is available as to whether aprotinin binds other types of amyloid fibrils and on the nature and characteristics of the interaction. The present work shows aprotinin binding to insulin, transthyretin, beta-amyloid peptide an d immunoglobulin synthetic amyloid fibrils by a specific dot-blot ligand-bi nding assay. Aprotinin did not bind amorphous precipitates and/or the solub le fibril precursors. A K-a of 2.9 mu m(-1) for the binding of aprotinin to insulin amyloid fibrils was determined by Scatchard analysis. In competiti on experiments, analogues such as an aprotinin variant, a spermadhesin and the soybean trypsin inhibitor were tested and results suggest that both apr otinin and the spermadhesin interact with amyloid fibrils through pairing o f beta-sheets of the ligands with exposed structures of the same type at th e surface of amyloid deposits. An electrostatic component may also be invol ved in the binding of aprotinin to amyloid fibrils because important differ ences in binding constants are observed when substitutions V15L17E52 are in troduced in aprotinin; on the other hand beta-sheet containing acidic prote ins, such as the soybean trypsin inhibitor, are unable to bind amyloid fibr ils.