Preprotein recognition by the Toc complex.
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.
Becker
Thomas
T
Botanik, LMU München, Germany.
Jelic
Marko
M
Vojta
Aleksandar
A
Radunz
Alfons
A
Soll
Jürgen
J
Schleiff
Enrico
E
D017360:Arabidopsis / Q000737:chemistry / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism; D002736:Chloroplasts / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008567:Membranes, Artificial; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology
D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D008567:Membranes, Artificial; D046912:Multiprotein Complexes; D010455:Peptides; D011498:Protein Precursors; C403444:TOC159 protein, Arabidopsis; C491798:TOC34 protein, Arabidopsis; C491244:TOC75 protein, Arabidopsis; D020558:GTP Phosphohydrolases