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-Structure paper
Title | Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes. |
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Journal, issue, pages | Cell, Vol. 185, Issue 25, Page 4788-4800.e13, Year 2022 |
Publish date | Dec 8, 2022 |
Authors | Zeyu Jin / Li Wan / Yuqi Zhang / Xuecheng Li / Yong Cao / Haobin Liu / Shengyao Fan / Du Cao / Zhengmao Wang / Xiaobo Li / Junmin Pan / Meng-Qiu Dong / Jianping Wu / Zhen Yan / |
PubMed Abstract | The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of chloroplast, but their exact molecular ...The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of chloroplast, but their exact molecular identities and assembly remain unclear. Here, we report a cryoelectron microscopy structure of TOC-TIC supercomplex from Chlamydomonas, containing a total of 14 identified components. The preprotein-conducting pore of TOC is a hybrid β-barrel co-assembled by Toc120 and Toc75, while the potential translocation path of TIC is formed by transmembrane helices from Tic20 and YlmG, rather than a classic model of Tic110. A rigid intermembrane space (IMS) scaffold bridges two chloroplast membranes, and a large hydrophilic cleft on the IMS scaffold connects TOC and TIC, forming a pathway for preprotein translocation. Our study provides structural insights into the TOC-TIC supercomplex composition, assembly, and preprotein translocation mechanism, and lays a foundation to interpret the evolutionary conservation and diversity of this fundamental translocon machinery. |
External links | Cell / PubMed:36413996 |
Methods | EM (single particle) |
Resolution | 2.5 Å |
Structure data | EMDB-31890, PDB-7vcf: |
Chemicals | ChemComp-LMG: ChemComp-IHP: ChemComp-MG: ChemComp-HOH: |
Source |
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Keywords | TRANSLOCASE / Complex / Channel |