Amide inequivalence in the fibrillar assembly of islet amyloid polypeptide
Amyloid fibers are aggregated, yet highly ordered, β-sheet-rich assemblies of misfolded proteins. Order is established in such systems following profiles indicative of nucleation-dependent assembly. Nucleation dependence suggests that specific interactions, such as long-range contacts and/or strand...
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Published in | Protein engineering, design and selection Vol. 21; no. 3; pp. 147 - 154 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
England
Oxford University Press
01.03.2008
Oxford Publishing Limited (England) |
Subjects | |
Online Access | Get full text |
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Summary: | Amyloid fibers are aggregated, yet highly ordered, β-sheet-rich assemblies of misfolded proteins. Order is established in such systems following profiles indicative of nucleation-dependent assembly. Nucleation dependence suggests that specific interactions, such as long-range contacts and/or strand registration, are critical to establishing initial fiber structure. Here, we show that amino acids at selected positions participate in key interactions that modulate the pathway of amyloid fiber formation by the hormone, islet amyloid polypeptide (IAPP). Specifically, we investigated the role of amide side-chain interactions in the process of IAPP assembly. We mutated five of the asparagine side chains in IAPP and assessed their effects on the kinetics of assembly. We find that the asparagine amide side chains strongly dictate the ability of IAPP to form fibers. In particular, the elimination of two specific asparagines results in near and total loss of amyloid, respectively. Interestingly, the two asparagines are located in a recently identified domain with α-helical bias. These sensitivities are unusual for IAPP, as IAPP is generally tolerant to mutation. Here, we demonstrate this mutational tolerance by assessing 10 alterations at five distinct sites. In all cases, the constructs form fibers on timescales perturbed by less than a factor of two compared with wild-type protein. These findings indicate the presence of key specific interactions that are the determinants of IAPP amyloid formation. |
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Bibliography: | istex:02E2C0FF30B53F34A4184ED8F868F2DCBCE0C0CD ark:/67375/HXZ-7HV8K8CH-F ArticleID:gzm076 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 1741-0126 1741-0134 |
DOI: | 10.1093/protein/gzm076 |