小柯机器人

中国科学院生物物理研究所柳振峰课题组报道叶绿体TOC-TIC转位子超复合物结构。相关论文于2023年1月26日在线发表于国际学术期刊《自然》。

研究人员报道了莱茵衣藻TOC-TIC超复合物的冷冻电镜结构，总分辨率为2.8Å的TOC复合体（Toc75、Toc90和Toc34）和TIC复合体（Tic214、Tic20、Tic100和Tic56）的主要亚基，3个叶绿体转位子相关蛋白（Ctap3、Ctap4和Ctap5）和3个新发现的膜内小蛋白（Simp1-3）均位于超复合体中。Tic214是最大的蛋白，它穿过细胞膜、膜间空间和外膜，将TOC复合物与TIC蛋白连接起来。六磷酸肌醇（InsP6或I6P）分子位于Tic214-Toc90界面并稳定它们的组装。此外，它们的脂质分子位于由Tic214、Tic20、Simp1和Ctap5组成的膜内漏斗内或上面。此外，在TOC-TIC超复合物中发现的多种潜在途径可能支持不同底物前蛋白转位到叶绿体中。

据悉，叶绿体依靠外膜和内膜的转位子复合物（分别称为TOC和TIC）从细胞质中输入不同核编码蛋白的基因。虽然先前的研究表明TOC和TIC复合物可以组装成更大的超复合物，但TOC-TIC超复合物的整体结构和前蛋白易位机制是不确定的。

附：英文原文

Title: Architecture of chloroplast TOC-TIC translocon supercomplex

Author: Liu, Hao, Li, Anjie, Rochaix, Jean-David, Liu, Zhenfeng

Issue&Volume: 2023-01-26

Abstract: Chloroplasts rely on the translocon complexes in the outer and inner envelope membranes (termed TOC and TIC, respectively) to import thousands of different nuclear-encoded proteins from the cytosol1-4. While previous studies indicated that the TOC and TIC complexes may assemble into larger supercomplexes5-7, the overall architectures of the TOC-TIC supercomplexes and the mechanism of preprotein translocation are elusive. Here we report the cryo-electron microscopy (cryo-EM) structure of the TOC-TIC supercomplex from Chlamydomonas reinhardtii at an overall resolution of 2.8 . The major subunits of the TOC complex (Toc75, Toc90 and Toc34) and TIC complex (Tic214, Tic20, Tic100 and Tic56), three chloroplast translocon-associated proteins (Ctap3, Ctap4 and Ctap5) and three newly-identified small inner-membrane proteins (Simp1-3) have been located in the supercomplex. As the largest protein, Tic214 traverses the inner membrane, the intermembrane space and the outer membrane, connecting the TOC complex with the TIC proteins. An inositol hexaphosphate (InsP6 or I6P) molecule is located at the Tic214-Toc90 interface and stabilizes their assembly. Moreover, four lipid molecules are located within or above an inner-membrane funnel formed by Tic214, Tic20, Simp1 and Ctap5. Furthermore, multiple potential pathways found in the TOC-TIC supercomplex may support translocation of different substrate preproteins into chloroplasts.

DOI: 10.1038/s41586-023-05744-y

Source: https://www.nature.com/articles/s41586-023-05744-y

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
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