Analysis of the minimal amyloid-forming fragment of the islet amyloid polypeptide - An experimental support for the key role of the phenylalanine residue in amyloid formation

Citation
R. Azriel et E. Gazit, Analysis of the minimal amyloid-forming fragment of the islet amyloid polypeptide - An experimental support for the key role of the phenylalanine residue in amyloid formation, J BIOL CHEM, 276(36), 2001, pp. 34156-34161
Citations number
49
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
276
Issue
36
Year of publication
2001
Pages
34156 - 34161
Database
ISI
SICI code
0021-9258(20010907)276:36<34156:AOTMAF>2.0.ZU;2-8
Abstract
The development of type Il diabetes was shown to be associated with the for mation of amyloid fibrils consisted of the islet amyloid polypeptide (IAPP or amylin). Recently, a short functional hexapeptide fragment of IAPP (NH2- NFGAIL-COOH) was found to form fibrils that are very similar to those forme d by the full-length polypeptide. To better understand the specific role of the residues that compose the fragment, we performed a systematic alanine scan of the LAPP "basic amyloidogenic units." Turbidity assay experiments d emonstrated that the wild-type peptide and the Asn(1) --> Ala and Gly(3) -- > Ala peptides had the highest rate of aggregate formation, whereas the Phe (2) --> Ala peptide did not form any detectable aggregates. Dynamic light-s cattering experiments demonstrated that all peptides except the Phe(2) --> Ala form large multimeric structures. Electron microscopy and Congo red sta ining confirmed that the structures formed by the various peptides are inde ed amyloid fibrils. Taken together, the results of our study provide clear experimental evidence for the key role of phenylalanine residue in amyloid formation by IAPP. In contrast, glycine, a residue that was suggested to fa cilitate amyloid formation in other systems, has only a minor role, if any, in this case. Our results are discussed in the context, of the remarkable occurrence of aromatic residues in short functional fragments and potent in hibitors of amyloid-related polypeptides. We hypothesize that pi-pi interac tions may play a significant role in the molecular recognition and self-ass embly processes that lead to amyloid formation.