The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

ONeil Patrick K.; Richardson Lynn G. L.; Paila Yamuna D.Piszczek GrzegorzChakravarthy SrinivasNoinaj NicholasSchnell Danny

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The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

机译：The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

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Protein trafficking across membranes is an essential function in cells; however, the exact mechanism for how this occurs is not well understood. In the endosymbionts, mitochondria and chloroplasts, the vast majority of proteins are synthesized in the cytoplasm as preproteins and then imported into the organelles via specialized machineries. In chloroplasts, protein import is accomplished by the TOC (translocon on the outer chloroplast membrane) and TIC (translocon on the inner chloroplast membrane) machineries in the outer and inner envelope membranes, respectively. TOC mediates initial recognition of preproteins at the outer membrane and includes a core membrane channel, Toc75, and two receptor proteins, Toc33/34 and Toc159, each containing GTPase domains that control preprotein binding and translocation. Toc75 is predicted to have a beta-barrel fold consisting of an N-terminal intermembrane space (IMS) domain and a C-terminal 16-stranded beta-barrel domain. Here we report the crystal structure of the N-terminal IMS domain of Toc75 from Arabidopsis thaliana, revealing three tandem polypeptide transportassociated (POTRA) domains, with POTRA2 containing an additional elongated helix not observed previously in other POTRA domains. Functional studies show an interaction with the preprotein, preSSU, which is mediated through POTRA2-3. POTRA2-3 also was found to have chaperone-like activity in an insulin aggregation assay, which we propose facilitates preprotein import. Our data suggest a model in which the POTRA domains serve as a binding site for the preprotein as it emerges from the Toc75 channel and provide a chaperonelike activity to prevent misfolding or aggregation as the preprotein traverses the intermembrane space.

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《Proceedings of the National Academy of Sciences of the United States of America.》 |2017年第24期|E4868-E4876|共9页
作者
ONeil Patrick K.; Richardson Lynn G. L.; Paila Yamuna D.Piszczek GrzegorzChakravarthy SrinivasNoinaj NicholasSchnell Danny;
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作者单位

Michigan State Univ, Dept Plant Biol, E Lansing, MI 48824 USA;

IIT, Argonne Natl Lab, Adv Photon Source, Biophys Collaborat Access Team, Sect 18ID, Argonne, IL 60439 USA;

Purdue Univ, Markey Ctr Struct Biol, Dept Biol Sci, W Lafayette, IN 47907 USANHLBI, NIH, Bldg 10, Bethesda, MD 20892 USA;

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收录信息美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
原文格式 PDF
正文语种英语
中图分类自然科学总论;
关键词
protein import; chloroplast; outer membrane; Toc75; POTRA domain;

The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts

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