Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 23, 2011 | Accepted Version + Supplemental Material
Journal Article Open

Concerted Complex Assembly and GTPase Activation in the Chloroplast Signal Recognition Particle


The universally conserved signal recognition particle (SRP) and SRP receptor (SR) mediate the cotranslational targeting of proteins to cellular membranes. In contrast, a unique chloroplast SRP in green plants is primarily dedicated to the post-translational targeting of light harvesting chlorophyll a/b binding (LHC) proteins. In both pathways, dimerization and activation between the SRP and SR GTPases mediate the delivery of cargo; whether and how the GTPase cycle in each system adapts to its distinct substrate proteins were unclear. Here, we show that interactions at the active site essential for GTPase activation in the chloroplast SRP and SR play key roles in the assembly of the GTPase complex. In contrast to their cytosolic homologues, GTPase activation in the chloroplast SRP–SR complex contributes marginally to the targeting of LHC proteins. These results demonstrate that complex assembly and GTPase activation are highly coupled in the chloroplast SRP and SR and suggest that the chloroplast GTPases may forego the GTPase activation step as a key regulatory point. These features may reflect adaptations of the chloroplast SRP to the delivery of their unique substrate protein.

Additional Information

© 2011 American Chemical Society. Received: May 12, 2011. Revised: July 21, 2011. Publication Date (Web): July 22, 2011. We thank X. Zhang, N. Pierce, and members of the Shan lab for helpful comments on the manuscript. This work was supported by NIH grant GM078024 to S.S. S.S. was supported by the Beckman Young Investigator award, the Packard and Lucile Award in Science and Engineering, and the Henry Dreyfus Teacher-Scholar Award.

Attached Files

Accepted Version - nihms-1001159.pdf

Supplemental Material - bi200742a_si_001.pdf


Files (1.6 MB)
Name Size Download all
929.2 kB Preview Download
702.5 kB Preview Download

Additional details

August 19, 2023
October 24, 2023