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Published June 8, 2018 | Published + Accepted Version + Supplemental Material
Journal Article Open

Two Distinct Sites of client protein interaction with the chaperone cpSRP43


Integral membrane proteins are prone to aggregation and misfolding in aqueous environments and therefore require binding by molecular chaperones during their biogenesis. Chloroplast signal recognition particle 43 (cpSRP43) is an ATP-independent chaperone required for the biogenesis of the most abundant class of membrane proteins, the light-harvesting chlorophyll a/b-binding proteins (LHCPs). Previous work has shown that cpSRP43 specifically recognizes an L18 loop sequence conserved among LHCP paralogs. However, how cpSRP43 protects the transmembrane domains (TMDs) of LHCP from aggregation was unclear. In this work, alkylation-protection and site-specific cross-linking experiments found that cpSRP43 makes extensive contacts with all the TMDs in LHCP. Site-directed mutagenesis identified a class of cpSRP43 mutants that bind tightly to the L18 sequence but are defective in chaperoning full-length LHCP. These mutations mapped to hydrophobic surfaces on or near the bridging helix and the β-hairpins lining the ankyrin repeat motifs of cpSRP43, suggesting that these regions are potential sites for interaction with the client TMDs. Our results suggest a working model for client protein interactions in this membrane protein chaperone.

Additional Information

© 2018 Published under license by The American Society for Biochemistry and Molecular Biology, Inc. Received for publication, February 3, 2018, and in revised form, March 29, 2018 Published, Papers in Press, April 18, 2018. This work was supported by Betty and Gordon Moore Foundation Grant 94-3397785 and National Institutes of Health Grant R01 GM114390 (to S.-o. S.) and by National Institutes of Health Training Grant 2 T32 GM 7616-36 (to C. Z. M.). 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 group for helpful comments on the manuscript. The Proteome Exploration Laboratory was supported by Betty and Gordon Moore Foundation Grant GBMF775 and the Beckman Institute at Caltech. Author contributions—C. Z. M., A. S., S. P., E. M., T. N., A. M., M. J. S., and S. H. data curation; C. Z. M., A. S., S. P., E. M., M. Y., T. N., A. M., S. H., and S.-o. S. formal analysis; C. Z. M., A. S., S. P., E. M., M. Y., T. N., and S. H. investigation; C. M. writing-original draft; A. S. and S.-o. S. validation; A. S., S. H., and S.-o. S. writing-review and editing; M. J. S. software; S. H. and S.-o. S. supervision; S.-o. S. conceptualization; S.-o. S. funding acquisition; S.-o. S. project administration.

Attached Files

Published - J._Biol._Chem.-2018-McAvoy-8861-73.pdf

Accepted Version - J._Biol._Chem.-2018-McAvoy-jbc.RA118.002215.pdf

Supplemental Material - 135723_1_supp_107935_p6dqkd.tif


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August 19, 2023
October 18, 2023