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Published January 6, 2017 | Published
Journal Article Open

Anionic Phospholipids and the Albino3 Translocase Activate Signal Recognition Particle-Receptor Interaction during Light-harvesting Chlorophyll a/b-binding Protein Targeting


The universally conserved signal recognition particle (SRP) co-translationally delivers newly synthesized membrane and secretory proteins to the target cellular membrane. The only exception is found in the chloroplast of green plants, where the chloroplast SRP (cpSRP) post-translationally targets light-harvesting chlorophyll a/b-binding proteins (LHCP) to the thylakoid membrane. The mechanism and regulation of this post-translational mode of targeting by cpSRP remain unclear. Using biochemical and biophysical methods, here we show that anionic phospholipids activate the cpSRP receptor cpFtsY to promote rapid and stable cpSRP54·cpFtsY complex assembly. Furthermore, the stromal domain of the Alb3 translocase binds with high affinity to and regulates GTP hydrolysis in the cpSRP54·cpFtsY complex, suggesting that cpFtsY is primarily responsible for initial recruitment of the targeting complex to Alb3. These results suggest a new model for the sequential recruitment, remodeling, and unloading of the targeting complex at membrane translocase sites in the post-translational cpSRP pathway.

Additional Information

© 2017 The American Society for Biochemistry and Molecular Biology, Inc. Under an Attribution 4.0 International (CC BY 4.0). Received August 9, 2016; Revision received October 14, 2016; First Published on November 28, 2016. This work was supported by National Institutes of Health Grant 1R01GM114390 and fellowships from the Gordon and Betty Moore Foundation and American Federation for Aging Research (to S. S.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We thank members of the Shan laboratory for comments on the manuscript. Author Contributions: S. S. conceived and coordinated the study and wrote the paper. S. C. designed, performed, and analyzed the experiments and wrote the paper. All authors reviewed the results and approved the final version of the manuscript.

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Published - J._Biol._Chem.-2017-Chandrasekar-397-406.pdf


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