Cytosolic chaperonin protects folding intermediates of Gbeta from aggregation by recognizing hydrophobic beta-strands.
Cytosolic chaperonin protects folding intermediates of Gbeta from aggregation by recognizing hydrophobic beta-strands.
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发表时间：
2006
影响因子：
11.1
通讯作者：
S. Kubota;H. Kubota;K. Nagata
中科院分区：
文献类型：
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作者：
S. Kubota;H. Kubota;K. Nagata
含有 t 复合物多肽 1 (CCT)/TRiC 的胞质伴侣蛋白是 II 族伴侣蛋白，有助于新合成蛋白质的折叠。它是 I 类细菌伴侣蛋白 GroEL 的真核同源物。与 GroEL 已被充分研究的功能相比，CCT/TRiC 的底物识别机制却知之甚少。在这里，我们建立了一个通过使用重组元件系统进行重建蛋白质合成来分析 CCT/TRiC 功能的系统，并表明 CCT/TRiC 强烈识别 WD40 蛋白质，特别是在疏水性 β 链处。使用 G 蛋白 β 亚基 (Gbeta)（一种富含 β 折叠的 WD40 蛋白）作为模型底物，我们发现 CCT/TRiC 可以防止 Gbeta 聚集并协助折叠，而 GroEL 则不能。 Gbeta拥有七叶β螺旋桨结构；每个叶片由编码四个 β 链的 WD40 重复序列形成。 Gbeta 的详细突变分析表明，CCT/TRiC（而非 GroEL）优先识别 Gbeta 的第二个 WD40 重复序列中 β 链表面上对齐的疏水残基。这些发现表明 CCT/TRiC 特异性靶标之一是疏水性 β 链，它极易聚集。
Cytosolic chaperonin containing t-complex polypeptide 1 (CCT)/TRiC is a group II chaperonin that assists in the folding of newly synthesized proteins. It is a eukaryotic homologue of the bacterial group I chaperonin GroEL. In contrast to the well studied functions of GroEL, the substrate recognition mechanism of CCT/TRiC is poorly understood. Here, we established a system for analyzing CCT/TRiC functions by using a reconstituted protein synthesis by using recombinant elements system and show that CCT/TRiC strongly recognizes WD40 proteins particularly at hydrophobic beta-strands. Using the G protein beta subunit (Gbeta), a WD40 protein that is very rich in beta-sheets, as a model substrate, we found that CCT/TRiC prevents aggregation and assists in folding of Gbeta, whereas GroEL does not. Gbeta has a seven-bladed beta-propeller structure; each blade is formed from a WD40 repeat sequence encoding four beta-strands. Detailed mutational analysis of Gbeta indicated that CCT/TRiC, but not GroEL, preferentially recognizes hydrophobic residues aligned on surfaces of beta-strands in the second WD40 repeat of Gbeta. These findings indicate that one of the CCT/TRiC-specific targets is hydrophobic beta-strands, which are highly prone to aggregation.