7VCF

Cryo-EM structure of Chlamydomonas TOC-TIC supercomplex

Summary for 7VCF

• Entry DOI: 10.2210/pdb7vcf/pdb
• EMDB information: 31890
• Descriptor: Tic214, Tic12, Unknown fragment, ... (19 entities in total)
• Functional Keywords: complex, translocase, channel
• Biological source: Chlamydomonas reinhardtii; More
• Total number of polymer chains: 15
• Total formula weight: 855697.12

Authors

Wu, J.,Yan, Z.,Jin, Z.,Zhang, Y. (deposition date: 2021-09-02, release date: 2022-11-30, Last modification date: 2025-07-02)

Primary citation

Jin, Z.,Wan, L.,Zhang, Y.,Li, X.,Cao, Y.,Liu, H.,Fan, S.,Cao, D.,Wang, Z.,Li, X.,Pan, J.,Dong, M.Q.,Wu, J.,Yan, Z.
Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes.
Cell, 185:4788-4800.e13, 2022

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 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.

PubMed: 36413996
DOI: 10.1016/j.cell.2022.10.030

Experimental method

ELECTRON MICROSCOPY (2.5 Å)