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Post-translational membrane protein targeting by the chloroplast signal recognition particle

Citation

Jaru-Ampornpan, Peera (2011) Post-translational membrane protein targeting by the chloroplast signal recognition particle. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05242011-165030719

Abstract

Post-translational transport of membrane proteins poses enormous challenges to the cells. The transport factors must accurately select and deliver the cargos to the appropriate target membranes. In addition, they have to provide chaperone for their hydrophobic cargos. To understand capacity and limitation of a post-translational transport factor, we studied one of the most efficient membrane protein transport pathways, the delivery of light-harvesting chlorophyll-binding (LHC) proteins to the thylakoid membrane. This targeting reaction is mediated by the chloroplast Signal Recognition Particle (cpSRP) and its receptor. Although the core SRP GTPases are close homologues of those in cytosolic SRP pathways, the unique features of cpSRP that might reflect its adaptation to the challenges in post-translational targeting include (i) the lack of the otherwise universally conserved SRP RNA, and (ii) the exclusive presence of a novel protein, cpSRP43. In the first part of this thesis, we define the thermodynamic and kinetic framework for the GTPase cycles of cpSRP and its receptor and uncover the molecular bases that enable their intrinsically fast interactions, such that they can bypass an SRP RNA, an essential accelerator for the cytosolic SRP–receptor interaction. The second part of the thesis is devoted to characterization of the chaperone function of cpSRP43. We show that cpSRP43 specifically and effectively prevents and reverses the aggregation of its cargo, LHC proteins. We further investigate the molecular mechanism of this novel disaggregase activity, using a combination of biochemical and structural approaches. In summary, this dissertation aims to understand how cpSRP and its receptor adapt to their unique requirements in efficiently transporting a family of highly abundant membrane proteins.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Protein targeting, Molecular chaperone, protein aggregate, Disaggregase
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Biochemistry and Molecular Biophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Shan, Shu-ou
Thesis Committee:
  • Rees, Douglas C. (chair)
  • Chan, David C.
  • Clemons, William M.
  • Shan, Shu-ou
Defense Date:29 April 2011
Record Number:CaltechTHESIS:05242011-165030719
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05242011-165030719
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6429
Collection:CaltechTHESIS
Deposited By: Peera Jaru-Ampornpan
Deposited On:27 May 2011 21:06
Last Modified:16 Apr 2013 23:00

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