Measurement of solubility product in a model condensate reveals the interplay of small oligomerization and self-association.
Measurement of solubility product in a model condensate reveals the interplay of small oligomerization and self-association.
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模型冷凝物中溶度积的测量揭示了小寡聚和自缔合的相互作用。
DOI：
10.1101/2024.01.23.576869
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发表时间：
2024
期刊：
影响因子：
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通讯作者：
Ditlev,JonathonA
中科院分区：
文献类型：
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作者：
Chattaraj,Aniruddha;Baltaci,Zeynep;Mayer,BruceJ;Loew,LeslieM;Ditlev,JonathonA
细胞凝聚物通常由10到100个不同的相互作用分子种类组成。由于这些相互作用的复杂性，预测它们将经历相分离成离散隔室的点是令人生畏的。使用实验和计算，因此，我们研究了一个简单的模型系统组成的2个蛋白质，聚SH 3和聚PRM，设计用于五价异型结合。我们测试了峰值溶度积（稀相单体浓度的乘积）是否是相分离开始的预测参数。滴定相等的总浓度的每一个组成部分表明，最大的溶度积近似符合相分离的实验和模型中的阈值。然而，我们发现，稀相浓度的测量包括小的低聚物，而不仅仅是单体的贡献，因此，定量比较的实验和模型需要包括小的低聚物的模型分析。我们还检查了完整的相图，其中模型结果几乎沿着对角线沿着对称，但实验结果高度不对称。这使我们进行了动态光散射实验，在那里我们发现了polyPRM的弱同型相互作用;当将其添加到计算模型中时，它能够概括实验观察到的不对称性。因此，比较实验模拟表明，溶解度积可以预测相分离，即使小的低聚物和低亲和力的同型相互作用排除实验测量单体浓度。
Cellular condensates often consist of 10s to 100s of distinct interacting molecular species. Because of the complexity of these interactions, predicting the point at which they will undergo phase separation into discrete compartments is daunting. Using experiments and computation, we therefore studied a simple model system consisting of 2 proteins, polySH3 and polyPRM, designed for pentavalent heterotypic binding. We tested whether the peak solubility product, the product of dilute phase monomer concentrations, is a predictive parameter for the onset of phase separation. Titrating up equal total concentrations of each component showed that the maximum solubility product does approximately coincide with the threshold for phase separation in both the experiments and models. However, we found that measurements of dilute phase concentration include contributions from small oligomers, not just monomers; therefore, a quantitative comparison of the experiments and models required inclusion of small oligomers in the model analysis. We also examined full phase diagrams where the model results were almost symmetric along the diagonal, but the experimental results were highly asymmetric. This led us to perform dynamic light scattering experiments, where we discovered a weak homotypic interaction for polyPRM; when this was added to the computational model, it was able to recapitulate the experimentally observed asymmetry. Thus, comparing experiments to simulation reveals that the solubility product can be predictive of phase separation, even if small oligomers and low affinity homotypic interactions preclude experimental measurement of monomer concentration.