Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States.
J Phys Chem Lett. 2024 Jun 20;15(24):6375-6382. doi: 10.1021/acs.jpclett.4c01410. Epub 2024 Jun 10.
The effects of two macromolecular cosolutes, specifically the polysaccharide dextran-20 and the protein lysozyme, on the aggregation kinetics of a pathogenic huntingtin exon-1 protein (hht) with a 35 polyglutamine repeat, httQ, are described. A unified kinetic model that establishes a direct connection between reversible tetramerization occurring on the microsecond time scale and irreversible fibril formation on a time scale of hours/days forms the basis for quantitative analysis of httQ aggregation, monitored by measuring cross-peak intensities in a series of 2D H-N NMR correlation spectra acquired during the course of aggregation. The primary effects of the two cosolutes are associated with shifts in the prenucleation tetramerization equilibrium resulting in substantial changes in concentration of "preformed" httQ tetramers. Similar effects of the two cosolutes on the tetramerization equilibrium observed for a shorter, nonaggregating huntingtin variant with a 7-glutamine repeat, httQ, lend confidence to the conclusions drawn from the fits to the httQ aggregation kinetics.
本文描述了两种高分子共溶剂（葡聚糖-20 和溶菌酶）对具有 35 个聚谷氨酰胺重复序列的致病性亨廷顿蛋白外显子-1（httQ）的聚集动力学的影响。一个统一的动力学模型建立了在微秒时间尺度上发生的可逆四聚体化与在小时/天时间尺度上发生的不可逆纤维形成之间的直接联系，为定量分析 httQ 聚集提供了基础，通过测量在聚集过程中获得的一系列二维 H-NMR 相关光谱中的交叉峰强度来监测 httQ 聚集。这两种共溶剂的主要影响与预成核四聚体化平衡的移动有关，导致“预成”httQ 四聚体的浓度发生实质性变化。对于具有 7 个谷氨酰胺重复序列的较短、不聚集的亨廷顿变体 httQ，观察到的两种共溶剂对四聚体化平衡的类似影响，为从 httQ 聚集动力学拟合中得出的结论提供了信心。
