Abstract
The Toc core complex consists of the pore-forming Toc75 and the GTPases Toc159 and Toc34. We confirm that the receptor form of Toc159 is integrated into the membrane. The association of Toc34 to Toc75/Toc159 is GTP dependent and enhanced by preprotein interaction. The N-terminal half of the pSSU transit peptide interacts with high affinity with Toc159, whereas the C-terminal part stimulates its GTP hydrolysis. The phosphorylated C-terminal peptide of pSSU interacts strongly with Toc34 and therefore inhibits binding and translocation of pSSU into Toc proteoliposomes. In contrast, Toc159 recognises only the dephosphorylated forms. The N-terminal part of the pSSU presequence does not influence binding to the Toc complex, but is able to block import into proteoliposomes through its interaction with Toc159. We developed a model of differential presequence recognition by Toc34 and Toc159.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Arabidopsis / chemistry
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Arabidopsis / physiology*
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Arabidopsis Proteins / chemistry
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Arabidopsis Proteins / metabolism
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Chloroplasts / chemistry
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Chloroplasts / metabolism*
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Chloroplasts / ultrastructure
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GTP Phosphohydrolases / chemistry
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GTP Phosphohydrolases / metabolism
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Intracellular Membranes / chemistry
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Intracellular Membranes / metabolism
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Intracellular Membranes / ultrastructure
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Membrane Proteins / chemistry
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Membrane Proteins / metabolism
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Membranes, Artificial
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Multiprotein Complexes / chemistry
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Multiprotein Complexes / metabolism*
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Peptides / chemistry
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Peptides / metabolism
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Plant Leaves / chemistry
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Plant Leaves / metabolism*
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Plant Leaves / ultrastructure
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Protein Binding
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Protein Precursors / chemistry
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Protein Precursors / metabolism
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Protein Transport / physiology
Substances
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Arabidopsis Proteins
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Membrane Proteins
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Membranes, Artificial
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Multiprotein Complexes
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Peptides
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Protein Precursors
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TOC159 protein, Arabidopsis
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TOC34 protein, Arabidopsis
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TOC75 protein, Arabidopsis
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GTP Phosphohydrolases