Jo Yongsang, Jang Jinyoung, Song Daesun, Park Hyoin, Jung Yongwon
Department of Chemistry, KAIST 291 Daehak-ro, Yuseong-gu Daejeon 34141 Republic of Korea
Chem Sci. 2021 Dec 16;13(2):522-530. doi: 10.1039/d1sc05672g. eCollection 2022 Jan 5.
Multivalent interactions between amino acid residues of intrinsically disordered proteins (IDPs) drive phase separation of these proteins into liquid condensates, forming various membrane-less organelles in cells. These interactions between often biased residues of IDPs are also likely involved in selective recruitment of many other IDPs into condensates. However, determining factors for this IDP recruitment into protein condensates are not understood yet. Here, we quantitatively examined recruitment tendencies of various IDPs with different sequence compositions into IDP-clustered condensates both as well as in cells. Condensate-forming IDP scaffolds, recruited IDP clients, and phase separation conditions were carefully varied to find key factors for selective IDP partitioning in protein condensates. Regardless of scaffold sequences, charged residues in client IDPs assured potent IDP recruitment, likely strong electrostatic interactions, where positive residues could further enhance recruitment, possibly with cation-pi interactions. Notably, poly-ethylene glycol, a widely used crowding reagent for phase separation, abnormally increased IDP recruitment, indicating the need for careful use of crowding conditions. Tyrosines of IDP clients also strongly participated in recruitment both and in cells. Lastly, we measured recruitment degrees by more conventional interactions between folded proteins instead of disordered proteins. Surprisingly, recruitment forces by an even moderate protein interaction ( ∼ 5 μM) were substantially stronger than those by natural IDP-IDP interactions. The present data offer valuable information on how cells might organize protein partitioning on various protein condensates.
内在无序蛋白（IDP）的氨基酸残基之间的多价相互作用驱动这些蛋白相分离形成液体凝聚物，在细胞中形成各种无膜细胞器。IDP中通常有偏向性的残基之间的这些相互作用也可能参与了许多其他IDP向凝聚物中的选择性募集。然而，IDP募集到蛋白凝聚物中的决定因素尚不清楚。在这里，我们定量研究了具有不同序列组成的各种IDP在IDP聚集的凝聚物中以及在细胞中的募集倾向。仔细改变形成凝聚物的IDP支架、募集的IDP客户和相分离条件，以找到蛋白凝聚物中IDP选择性分配的关键因素。无论支架序列如何，客户IDP中的带电残基确保了有效的IDP募集，可能是由于强烈的静电相互作用，其中带正电的残基可能通过阳离子-π相互作用进一步增强募集。值得注意的是，聚乙二醇是一种广泛用于相分离的拥挤试剂，它异常增加了IDP的募集，这表明需要谨慎使用拥挤条件。IDP客户中的酪氨酸在凝聚物中和细胞中也强烈参与募集。最后，我们通过折叠蛋白而非无序蛋白之间更传统的相互作用来测量募集程度。令人惊讶的是，即使是适度的蛋白相互作用（约5 μM）产生的募集力也比天然IDP-IDP相互作用产生的募集力强得多。目前的数据为细胞如何在各种蛋白凝聚物上组织蛋白分配提供了有价值的信息。
