Rights statement: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Biochemistry, copyright © 2017 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.biochem.6b01120
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Heparin and methionine oxidation promote the formation of apolipoprotein A-I amyloid comprising α-helical and β-sheet structures.
AU - Townsend, David John
AU - Hughes, Eleri
AU - Hussain, Rohanah
AU - Siligardi, Giuliano
AU - Baldock, Sara Jane
AU - Madine, Jillian
AU - Middleton, David Andrew
N1 - This document is the Accepted Manuscript version of a Published Work that appeared in final form in Biochemistry, copyright © 2017 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.biochem.6b01120
PY - 2017/3/21
Y1 - 2017/3/21
N2 - Peptides derived from apolipoprotein A-I (apoA-I), the main component of high-density lipoprotein (HDL), constitute the main component of amyloid deposits that co-localise with atherosclerotic plaques. Here we investigate the molecular details of full-length, lipid-deprived apoA-I after assembly into insoluble aggregates under physiologically-relevant conditions known to induce aggregation in vitro. Unmodified apoA-I is shown to remain soluble at pH 7 for at least 3 days, retaining its native α-helical-rich structure. Upon acidification to pH 4, apoA-I rapidly assembles into insoluble non-fibrillar aggregates lacking the characteristic cross-beta features of amyloid. In the presence of heparin, the rate and thioflavin T responsiveness of the aggregates formed at pH 4 increase and short amyloid-like fibrils are observed, which give rise to amyloid-characteristic X-ray reflections at 4.7 and 10 Å. Solid-state NMR (SSNMR) and synchrotron radiation circular dichroism (SRCD) spectroscopy of fibrils formed in the presence of heparin retain some α-helical characteristics together with new β-sheet structures. Interestingly, SSNMR and indicates a similar molecular structure of aggregates formed in the absence of heparin at pH 6 after oxidation of the three methionine residues, although their morphology is rather different from the heparin-derived fibrils. We propose a model for apoA-I aggregation in which perturbations of an 4-helix bundle-like structure, induced by interactions of heparin or methionine oxidation, cause the partially helical N-terminal residues to disengage from the remaining, intact helices, thereby allowing self-assembly via β-strand associations.
AB - Peptides derived from apolipoprotein A-I (apoA-I), the main component of high-density lipoprotein (HDL), constitute the main component of amyloid deposits that co-localise with atherosclerotic plaques. Here we investigate the molecular details of full-length, lipid-deprived apoA-I after assembly into insoluble aggregates under physiologically-relevant conditions known to induce aggregation in vitro. Unmodified apoA-I is shown to remain soluble at pH 7 for at least 3 days, retaining its native α-helical-rich structure. Upon acidification to pH 4, apoA-I rapidly assembles into insoluble non-fibrillar aggregates lacking the characteristic cross-beta features of amyloid. In the presence of heparin, the rate and thioflavin T responsiveness of the aggregates formed at pH 4 increase and short amyloid-like fibrils are observed, which give rise to amyloid-characteristic X-ray reflections at 4.7 and 10 Å. Solid-state NMR (SSNMR) and synchrotron radiation circular dichroism (SRCD) spectroscopy of fibrils formed in the presence of heparin retain some α-helical characteristics together with new β-sheet structures. Interestingly, SSNMR and indicates a similar molecular structure of aggregates formed in the absence of heparin at pH 6 after oxidation of the three methionine residues, although their morphology is rather different from the heparin-derived fibrils. We propose a model for apoA-I aggregation in which perturbations of an 4-helix bundle-like structure, induced by interactions of heparin or methionine oxidation, cause the partially helical N-terminal residues to disengage from the remaining, intact helices, thereby allowing self-assembly via β-strand associations.
U2 - 10.1021/acs.biochem.6b01120
DO - 10.1021/acs.biochem.6b01120
M3 - Journal article
VL - 56
SP - 1632
EP - 1644
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 11
ER -