The molecular basis for distinct pathways for protein import into Arabidopsis chloroplasts.
The translocons at the outer envelope membrane of chloroplasts (TOCs) initiate the import of thousands of nucleus-encoded proteins into the organelle. The identification of structurally and functionally distinct TOC complexes has led to the hypothesis that the translocons constitute different import pathways that are required to coordinate the import of sets of proteins whose expression varies in response to organelle biogenesis and physiological adaptation. To test this hypothesis, we examined the molecular basis for distinct TOC pathways by analyzing the functional diversification among the Toc159 family of TOC receptors. We demonstrate that the N-terminal A-domains of the Toc159 receptors regulate their selectivity for preprotein binding. Furthermore, the in vivo function of the two major Toc159 family members (atToc159 and atToc132) can be largely switched by swapping their A-domains in transgenic Arabidopsis thaliana. On the basis of these results, we propose that the A-domains of the Toc159 receptors are major determinants of distinct pathways for protein import into chloroplasts.
Inoue
Hitoshi
H
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Rounds
Caleb
C
Schnell
Danny J
DJ
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D018744:DNA, Plant / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport
D029681:Arabidopsis Proteins; D018744:DNA, Plant; D008565:Membrane Proteins; C403444:TOC159 protein, Arabidopsis; D020558:GTP Phosphohydrolases