Journal
JOURNAL OF CELL BIOLOGY
Volume 165, Issue 3, Pages 323-334Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200311074
Keywords
chloroplasts; protein transport; protein binding; cross-linking; GTPase
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Funding
- NIGMS NIH HHS [GM61893, R01 GM061893] Funding Source: Medline
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The members of the Toc159 family of GTPases act as the primary receptors for the import of nucleus-encoded preproteins into plastids. Toc-159, the most abundant member of this family in chloroplasts, is required for chloroplast biogenesis (Bauer, J., K. Chen, A. Hiltbunner, E. Wehrli, M. Eugster, D. Schnell, and F. Kessler. 2000. Nature. 403: 203-207) and has been shown to covalently cross-link to bound preproteins at the chloroplast surface (Ma, Y., A. Kouranov, S. LaSala, and D.J. Schnell. 1996. J. Cell Biol. 134:1-13; Perry, S.E., and K. Keegstra. 1994. Plant Cell. 6:93-105). These reports led to the hypothesis that Toc159 functions as a selective import receptor for preproteins that are required for chloroplast development. In this report, we provide evidence that Toc159 is required for the import of several highly expressed photosynthetic preproteins in vivo. Furthermore, we demonstrate that the cytoplasmic and recombinant forms of soluble Toc159 bind directly and selectively to the transit peptides of these representative photosynthetic preproteins, but not representative constitutively expressed plastid preproteins. These data support the function of Toc159 as a selective import receptor for the targeting of a set of preproteins required for chloroplast biogenesis.
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