Cargando…

Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP

Human islet amyloid polypeptide (hIAPP) aggregates into fibrils through oligomers that have been postulated to contain α-helices as well as β-sheets. We employ a site-specific isotope labeling strategy that is capable of detecting changes in dihedral angles when used in conjunction with 2D IR spectr...

Descripción completa

Detalles Bibliográficos
Autores principales: Maj, Michał, Lomont, Justin P., Rich, Kacie L., Alperstein, Ariel M., Zanni, Martin T.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Royal Society of Chemistry 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868010/
https://www.ncbi.nlm.nih.gov/pubmed/29619202
http://dx.doi.org/10.1039/c7sc03789a
_version_ 1783309068980453376
author Maj, Michał
Lomont, Justin P.
Rich, Kacie L.
Alperstein, Ariel M.
Zanni, Martin T.
author_facet Maj, Michał
Lomont, Justin P.
Rich, Kacie L.
Alperstein, Ariel M.
Zanni, Martin T.
author_sort Maj, Michał
collection PubMed
description Human islet amyloid polypeptide (hIAPP) aggregates into fibrils through oligomers that have been postulated to contain α-helices as well as β-sheets. We employ a site-specific isotope labeling strategy that is capable of detecting changes in dihedral angles when used in conjunction with 2D IR spectroscopy. The method is analogous to the chemical shift index used in NMR spectroscopy for assigning protein secondary structure. We introduce isotope labels at two neighbouring residues, which results in an increased intensity and positive frequency shift if those residues are α-helical versus a negative frequency shift in β-sheets and turns. The 2D IR dihedral index approach is demonstrated for hIAPP in micelles for which the polypeptide structure is known, using pairs of (13)C(18)O isotope labels L12A13 and L16V17, along with single labeled control experiments. Applying the approach to aggregation experiments performed in buffer, we show that about 27–38% of hIAPP peptides adopt an α-helix secondary structure in the monomeric state at L12A13, prior to aggregation, but not at L16V17 residues. At L16V17, the kinetics are described solely by the monomer and fiber conformations, but at L12A13 the kinetics exhibit a third state that is created by an oligomeric intermediate. Control experiments performed with a single isotope label at A13 exhibit two-state kinetics, indicating that a previously unknown change in dihedral angle occurs at L12A13 as hIAPP transitions from the intermediate to fiber structures. We propose a mechanism for aggregation, in which helices seed oligomer formation via structures analogous to leucine rich repeat proteins.
format Online
Article
Text
id pubmed-5868010
institution National Center for Biotechnology Information
language English
publishDate 2017
publisher Royal Society of Chemistry
record_format MEDLINE/PubMed
spelling pubmed-58680102018-04-04 Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP Maj, Michał Lomont, Justin P. Rich, Kacie L. Alperstein, Ariel M. Zanni, Martin T. Chem Sci Chemistry Human islet amyloid polypeptide (hIAPP) aggregates into fibrils through oligomers that have been postulated to contain α-helices as well as β-sheets. We employ a site-specific isotope labeling strategy that is capable of detecting changes in dihedral angles when used in conjunction with 2D IR spectroscopy. The method is analogous to the chemical shift index used in NMR spectroscopy for assigning protein secondary structure. We introduce isotope labels at two neighbouring residues, which results in an increased intensity and positive frequency shift if those residues are α-helical versus a negative frequency shift in β-sheets and turns. The 2D IR dihedral index approach is demonstrated for hIAPP in micelles for which the polypeptide structure is known, using pairs of (13)C(18)O isotope labels L12A13 and L16V17, along with single labeled control experiments. Applying the approach to aggregation experiments performed in buffer, we show that about 27–38% of hIAPP peptides adopt an α-helix secondary structure in the monomeric state at L12A13, prior to aggregation, but not at L16V17 residues. At L16V17, the kinetics are described solely by the monomer and fiber conformations, but at L12A13 the kinetics exhibit a third state that is created by an oligomeric intermediate. Control experiments performed with a single isotope label at A13 exhibit two-state kinetics, indicating that a previously unknown change in dihedral angle occurs at L12A13 as hIAPP transitions from the intermediate to fiber structures. We propose a mechanism for aggregation, in which helices seed oligomer formation via structures analogous to leucine rich repeat proteins. Royal Society of Chemistry 2017-11-03 /pmc/articles/PMC5868010/ /pubmed/29619202 http://dx.doi.org/10.1039/c7sc03789a Text en This journal is © The Royal Society of Chemistry 2018 http://creativecommons.org/licenses/by/3.0/ This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0)
spellingShingle Chemistry
Maj, Michał
Lomont, Justin P.
Rich, Kacie L.
Alperstein, Ariel M.
Zanni, Martin T.
Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title_full Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title_fullStr Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title_full_unstemmed Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title_short Site-specific detection of protein secondary structure using 2D IR dihedral indexing: a proposed assembly mechanism of oligomeric hIAPP
title_sort site-specific detection of protein secondary structure using 2d ir dihedral indexing: a proposed assembly mechanism of oligomeric hiapp
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868010/
https://www.ncbi.nlm.nih.gov/pubmed/29619202
http://dx.doi.org/10.1039/c7sc03789a
work_keys_str_mv AT majmichał sitespecificdetectionofproteinsecondarystructureusing2dirdihedralindexingaproposedassemblymechanismofoligomerichiapp
AT lomontjustinp sitespecificdetectionofproteinsecondarystructureusing2dirdihedralindexingaproposedassemblymechanismofoligomerichiapp
AT richkaciel sitespecificdetectionofproteinsecondarystructureusing2dirdihedralindexingaproposedassemblymechanismofoligomerichiapp
AT alpersteinarielm sitespecificdetectionofproteinsecondarystructureusing2dirdihedralindexingaproposedassemblymechanismofoligomerichiapp
AT zannimartint sitespecificdetectionofproteinsecondarystructureusing2dirdihedralindexingaproposedassemblymechanismofoligomerichiapp