Phosphorylation regulates the assembly of chloroplast import machinery

  • Chloroplast function depends on the translocation of cytosolically synthesized precursor proteins into the organelle. The recognition and transfer of most precursor proteins across the outer membrane depend on a membrane inserted complex. Two receptor components of this complex, Toc34 and Toc159, are GTPases, which can be phosphorylated by kinases present in the hosting membrane. However, the physiological function of phosphorylation is not yet understood in detail. It is demonstrated that both receptors are phosphorylated within their G-domains. In vitro, the phosphorylation of Toc34 disrupts both homo- and heterodimerization of the G-domains as determined using a phospho-mimicking mutant. In endogenous membranes this mutation or phosphorylation of the wild-type receptor disturbs the association of Toc34, but not of Toc159 with the translocation pore. Therefore, phosphorylation serves as an inhibitor for the association of Toc34 with other components of the complex and phosphorylation can now be discussed as a mechanism to exchange different isoforms of Toc34 within this ensemble.

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Author:Igor-Mislav OrebORCiDGND, Anja Höfle, Oliver MirusGND, Enrico SchleiffORCiDGND
Pubmed Id:
Parent Title (English):The journal of experimental botany
Publisher:Oxford University Press
Place of publication:Oxford
Document Type:Article
Date of Publication (online):2008/10/01
Date of first Publication:2008/05/17
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2008/10/01
Tag:GTPase; TOC; membrane complex dynamics; phosphorylation; plastids; protein complex assembly; protein translocation
Page Number:18
First Page:2309
Last Page:2316
ª 2008 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Institutes:Biowissenschaften / Biowissenschaften
Wissenschaftliche Zentren und koordinierte Programme / Center for Membrane Proteomics (CMP)
Exzellenzcluster / Exzellenzcluster Makromolekulare Komplexe
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Sammlungen:Sammlung Biologie / Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung-Nicht kommerziell 2.0