Structural Features and Domain Organization of Huntingtin Fibrils

被引:72
作者
Bugg, Charles W. [2 ]
Isas, J. Mario [1 ]
Fischer, Torsten [1 ]
Patterson, Paul H. [2 ]
Langen, Ralf [1 ]
机构
[1] Univ So Calif, Dept Biochem & Mol Biol, Zilkha Neurogenet Inst, Keck Sch Med, Los Angeles, CA 90089 USA
[2] CALTECH, Div Biol, Pasadena, CA 91125 USA
基金
美国国家卫生研究院;
关键词
PROTEIN SECONDARY STRUCTURE; CIRCULAR-DICHROISM SPECTRA; BETA-SHEET STRUCTURE; IN-VITRO; POLYGLUTAMINE AGGREGATION; INTRANUCLEAR INCLUSIONS; EXPANDED GLUTAMINE; MUTANT HUNTINGTIN; ALPHA-SYNUCLEIN; CAG REPEAT;
D O I
10.1074/jbc.M112.353839
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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 angstrom 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.
引用
收藏
页码:31739 / 31746
页数:8
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