Structures of Ric-8B in complex with Gα protein folding clients reveal isoform specificity mechanisms.
Structures of Ric-8B in complex with Gα protein folding clients reveal isoform specificity mechanisms.
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Ric-8B 与 Gα 蛋白折叠客户复合物的结构揭示了亚型特异性机制。
DOI：
10.1016/j.str.2023.02.011
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Tall,GregoryG
中科院分区：
文献类型：
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作者：
Papasergi-Scott,MakaíaM;Kwarcinski,FrankE;Yu,Maiya;Panova,Ouliana;Ovrutsky,AnnM;Skiniotis,Georgios;Tall,GregoryG
哺乳动物 Ric-8 蛋白作为伴侣来调节异源三聚体 G 蛋白 α 亚基的细胞丰度。 Ric-8A 同工型分子伴侣 Gαi/o、Gα12/13 和 Gαq/11 亚基，而 Ric-8B 作用于 Gαs/olf 亚基。在这里，我们确定了 Ric-8B 与 Gαs 和 Gαolf 复合物的冷冻电子显微镜 (cryo-EM) 结构，揭示了由 Ric-8 α-螺旋重复元件形成的凹口袋内 Gα 的 C 端 α5 螺旋之间的相对定位和接触的异构体差异。尽管总体结构与我们早期与 Gαq 和 Gαi1 复合的 Ric-8A 结构相似，但 Ric-8B 明显容纳了仅在 Gαs/olf 蛋白中发现的扩展环。这些结构以及 Ric-8 蛋白热稳定性测定和基于细胞的 Gαolf 折叠测定的结果支持 Gα C 末端区域实现结合特异性的要求，并强调多个结构元件赋予 Ric-8/G 蛋白结合特异性。
Mammalian Ric-8 proteins act as chaperones to regulate the cellular abundance of heterotrimeric G protein α subunits. The Ric-8A isoform chaperones Gαi/o, Gα12/13, and Gαq/11 subunits, while Ric-8B acts on Gαs/olf subunits. Here, we determined cryoelectron microscopy (cryo-EM) structures of Ric-8B in complex with Gαs and Gαolf, revealing isoform differences in the relative positioning and contacts between the C-terminal α5 helix of Gα within the concave pocket formed by Ric-8 α-helical repeat elements. Despite the overall architectural similarity with our earlier structures of Ric-8A complexed to Gαq and Gαi1, Ric-8B distinctly accommodates an extended loop found only in Gαs/olf proteins. The structures, along with results from Ric-8 protein thermal stability assays and cell-based Gαolf folding assays, support a requirement for the Gα C-terminal region for binding specificity, and highlight that multiple structural elements impart specificity for Ric-8/G protein binding.