Molecular Plant, 1 November, 2024, DOI：https://doi.org/10.1016/j.molp.2024.09.010

Architecture of the ATP-driven motor for protein import into chloroplasts

Ning Wang, Jiale Xing, Xiaodong Su, Junting Pan, Hui Chen, Lifang Shi, Long Si, Wenqiang Yang, Mei Li

Abstract

Thousands of nuclear-encoded proteins are transported into chloroplasts through the TOC–TIC translocon that spans the chloroplast envelope membranes. A motor complex pulls the translocated proteins out of the TOC–TIC complex into the chloroplast stroma by hydrolyzing ATP. The Orf2971–FtsHi complex has been suggested to serve as the ATP-hydrolyzing motor in Chlamydomonas reinhardtii, but little is known about its architecture and assembly. Here, we report the 3.2-? resolution structure of the Chlamydomonas Orf2971–FtsHi complex. The 20-subunit complex spans the chloroplast inner envelope, with two bulky modules protruding into the intermembrane space and stromal matrix. Six subunits form a hetero-hexamer that potentially provides the pulling force through ATP hydrolysis. The remaining subunits, including potential enzymes/chaperones, likely facilitate the complex assembly and regulate its proper function. Taken together, our results provide the structural foundation for a mechanistic understanding of chloroplast protein translocation.

Article link：https://www.sciencedirect.com/science/article/pii/S1674205224002995