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标题：A distinct class of GTP-binding proteins mediates chloroplast protein import in Rhodophyta
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作者：Sanghun Baek ; Sousuke Imamura ; Takeshi Higa 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：34
DOI：10.1073/pnas.2208277119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Chloroplast protein import is mediated by translocons named TOC and TIC on the outer and inner envelope membranes, respectively. Translocon constituents are conserved among green lineages, including plants and green algae. However, it remains unclear whether Rhodophyta (red algae) share common chloroplast protein import mechanisms with the green lineages. We show that in the rhodophyte Cyanidioschyzon merolae, plastome-encoded Tic20 pt localized to the chloroplast envelope and was transiently associated with preproteins during import, suggesting its conserved function as a TIC constituent. Besides plastome-encoded FtsH pt and several chaperones, a class of GTP (guanosine 5′-triphosphate)-binding proteins distinct from the Toc34/159 GTPase family associated transiently with preproteins. This class of proteins resides mainly in the cytosol and shows sequence similarities with Sey1/RHD3, required for endoplasmic reticulum membrane fusion, and with the periplastid-localized import factor PPP1, previously identified in the Apicomplexa and diatoms. These GTP-binding proteins, named plastid targeting factor for protein import 1 (PTF1) to PTF3, may act as plastid targeting factors in Rhodophyta.
关键词：enchloroplast protein importorganelle biogenesisalgal evolutionintracellular protein trafficRhodophyta