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Structural Features and Domain Organization of Huntingtin Fibrils

Bugg, Charles W. and Isas, J. Mario and Fischer, Torsten and Patterson, Paul H. and Langen, Ralf (2012) Structural Features and Domain Organization of Huntingtin Fibrils. Journal of Biological Chemistry, 287 (38). pp. 31739-31746. ISSN 0021-9258. PMCID PMC3442508. doi:10.1074/jbc.M112.353839.

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Misfolding and aggregation of huntingtin is one of the hallmarks of Huntington disease, but the overall structure of these aggregates and the mechanisms by which huntingtin misfolds remain poorly understood. Here we used site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy to study the structural features of huntingtin exon 1 (HDx1) containing 46 glutamine residues in its polyglutamine (polyQ) region. Despite some residual structuring in the N terminus, we find that soluble HDx1 is highly dynamic. Upon aggregation, the polyQ domain becomes strongly immobilized indicating significant tertiary or quaternary packing interactions. Analysis of spin-spin interactions does not show the close contact between same residues that is characteristic of the parallel, in-register structure commonly found in amyloids. Nevertheless, the same residues are still within 20 Å of each other, suggesting that polyQ domains from different molecules come into proximity in the fibrils. The N terminus has previously been found to take up a helical structure in fibrils. We find that this domain not only becomes structured, but that it also engages in tertiary or quaternary packing interactions. The existence of spin-spin interactions in this region suggests that such contacts could be made between N-terminal domains from different molecules. In contrast, the C-terminal domain is dynamic, contains polyproline II structure, and lacks pronounced packing interactions. This region must be facing away from the core of the fibrils. Collectively, these data provide new constraints for building structural models of HDx1 fibrils.

Item Type:Article
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URLURL TypeDescription CentralArticle
Fischer, Torsten0000-0002-3365-8875
Additional Information:© 2012 by The American Society for Biochemistry and Molecular Biology, Inc. Received for publication, February 16, 2012, and in revised form, July 7, 2012 Published, JBC Papers in Press, July 16, 2012. This work was supported, in whole or in part, by a grant from the National Institutes of Health through the NINDS (to P. H. P.). This work was also supported by grants from the Hereditary Disease Foundation (to R. L. and P. H. P.). We thank Konstantin Piatkov for advice regarding protein purification and Ansgar Siemer for helpful discussion.
Funding AgencyGrant Number
National Institute of Neurological Disorders and Stroke (NINDS)UNSPECIFIED
Hereditary Disease FoundationUNSPECIFIED
Subject Keywords:Protein Structure and Folding
Issue or Number:38
PubMed Central ID:PMC3442508
Record Number:CaltechAUTHORS:20121130-090231098
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Official Citation:Charles W. Bugg, J. Mario Isas, Torsten Fischer, Paul H. Patterson, and Ralf Langen Structural Features and Domain Organization of Huntingtin Fibrils J. Biol. Chem. 2012 287: 31739-31746. doi:10.1074/jbc.M112.353839
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35741
Deposited By: Tony Diaz
Deposited On:30 Jan 2013 23:21
Last Modified:09 Nov 2021 23:17

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