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, ar...

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Bibliographic Details
Published in:Journal of experimental botany 2008-06, Vol.59 (9), p.2309-2316
Main Authors: Oreb, Mislav, Höfle, Anja, Mirus, Oliver, Schleiff, Enrico
Format: Article
Language:English
Subjects:
Antibodies
Arabidopsis - chemistry
Arabidopsis - genetics
Arabidopsis - metabolism
Arabidopsis Proteins - chemistry
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
Biochemistry
Biological and medical sciences
Cell motion
Cell physiology
Chloroplasts
Chloroplasts - metabolism
Dimerization
Fundamental and applied biological sciences. Psychology
GTP Phosphohydrolases - chemistry
GTP Phosphohydrolases - genetics
GTP Phosphohydrolases - metabolism
GTPase
membrane complex dynamics
Membrane Proteins - chemistry
Membrane Proteins - genetics
Membrane Proteins - metabolism
Models, Molecular
Peas
Phosphorylation
Physiological regulation
Plant physiology and development
Plastids
Protein Binding
protein complex assembly
Protein Structure, Tertiary
protein translocation
Protein Transport
Proteins
Receptors
Research Papers
TOC
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Summary: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.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/ern095