Single Amino Acid Substitutions in Stickers, but Not Spacers, Substantially Alter UBQLN2 Phase Transitions and Dense Phase Material Properties
Single Amino Acid Substitutions in Stickers, but Not Spacers, Substantially Alter UBQLN2 Phase Transitions and Dense Phase Material Properties
复制标题
贴纸中的单一氨基酸取代（而非间隔物）显着改变 UBQLN2 相变和密相材料特性
DOI：
10.1021/acs.jpcb.9b01024
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Castañeda, Carlos A.
中科院分区：
文献类型：
--
作者：
Yang, Yiran;Jones, Holly B.;Dao, Thuy P.;Castañeda, Carlos A.
UBQLN2 450-624寡聚并经历温度响应的液-液相变，遵循闭环温度-浓度相图。我们最近发现，UBQLN2 450-624的疾病相关突变对其相行为产生了高度不同的影响，从很小的变化到饱和浓度和凝胶和聚集体形成的显著降低。然而，单个突变如何导致这些特性尚不清楚。本文以UBQLN2 450-624为模型系统，研究了相分离的序列决定因素。我们假设UBQLN2 450-624区域是驱动链间相互作用和相分离的“贴纸”。我们系统地研究了19种可能的单氨基酸在3个贴片和2个“间隔”（分离贴片的序列）位置上的取代对相行为的影响。总的来说，取代贴纸，而不是间隔，实质上改变了相图的形状。在黏附区域内，疏水性的增加降低了低温下的饱和浓度，增强了致密相的寡聚倾向和粘弹性。相反，在所有位置上对酸性残基的取代大大增加了饱和浓度。我们的数据表明，单氨基酸取代遵循分子代码来调整生物聚合物的相变行为。
UBQLN2 450–624 oligomerizes and undergoes temperature-responsive liquid–liquid phase transitions following a closed-loop temperature–concentration phase diagram. We recently showed that disease-linked mutations to UBQLN2 450–624 impart highly varying effects to its phase behavior, ranging from little change to significant decrease of saturation concentration and formation of gels and aggregates. However, how single mutations lead to these properties is unknown. Here, we use UBQLN2 450–624 as a model system to study the sequence determinants of phase separation. We hypothesized that UBQLN2 450–624 regions previously identified to promote its oligomerization are the “stickers” that drive interchain interactions and phase separation. We systematically investigated how phase behavior is affected by all 19 possible single amino acid substitutions at three sticker and two “spacer” (sequences separating stickers) positions. Overall, substitutions to stickers, but not spacers, substantially altered the shape of the phase diagram. Within the sticker regions, increasing hydrophobicity decreased saturation concentrations at low temperatures and enhanced oligomerization propensity and viscoelasticity of the dense phase. Conversely, substitutions to acidic residues at all positions greatly increased saturation concentrations. Our data demonstrate that single amino acid substitutions follow a molecular code to tune phase transition behavior of biopolymers.