Korean Journal of Plant Tissue Culture (식물조직배양학회지)

The Korean Society of Plant Biotechnology (한국식물생명공학회)
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Targeting of Nuclear Encoded Proteins to Chloroplasts: a New Insight into the Mechanism

  • Lee, Yong-Jik (Division of Molecular and Life Sciences, Pohang University of Science and Technology, Center for Plant Intracellular Trafficking, Pohang University of Science and Technology) ;
  • Kim, Yong-Woo (Center for Plant Intracellular Trafficking, Pohang University of Science and Technology) ;
  • Pih, Kyeong-Tae (Center for Plant Intracellular Trafficking, Pohang University of Science and Technology) ;
  • Hwang, Inhwan (Division of Molecular and Life Sciences, Pohang University of Science and Technology, Center for Plant Intracellular Trafficking, Pohang University of Science and Technology)
  • Published : 2000.09.01
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Abstract

Outer envelope membrane proteins of chloroplasts encoded by the nuclear genome are transported without the N-terminal transit peptide. Here, we investigated the targeting mechanism of AtOEP7, an Arabidopsis homolog of small outer envelope membrane proteins in vivo. AtOEP7 was expressed transiently in protoplasts or stably in transgenic plants as fusion proteins with GFP. In both cases AtOEP7:GFP was targeted to the outer envelope membrane when assayed under a fluorescent microscope or by Western blot analysis. Except the transmembrane domain, deletions of the N- or C-terminal regions of AtOEP7 did not affect targeting although a region closed to the C-terminal side of the transmembrane domain affected the targeting efficiency. Targeting experiments with various hybrid transmembrane mutants revealed that the amino acid sequence of the transmembrane domain determines the targeting specificity The targeting mechanism was further studied using a fusion protein, AtOEP7：NLS：GFP, that had a nuclear localization signal. AtOEP7：NLS：GFP was efficiently targeted to the chloroplast envelope despite the presence of the nuclear localization signal. Taken together, these results suggest that the transmembrane domain of AtOEP7 functions as the sole determinant of targeting specificity and that AtOEP7 may be associated with a cytosolic component during translocation to the chloroplast envelope membrane.

Keywords

References

  1. J. Biol. Chem. v.272 Insertion of the 34-kDa chloroplast protein import component, IAP34, into the chloroplast outer membrane is dependent on its intrinsic GTP-binding capacity Chen, D.;Schnell, D.J.
  2. Plant Mol. Biol. v.36 Soluble, highly fluorescent variants of green fluorescent protein (GFP) for use in higher plants Davis, S.J.;Vierstra, R.D.
  3. EMBO J. v.8 The transit peptide of a chloroplast thylakoid membrane protein is functionally equivalent to a stromal-targeting sequence Hand, J.M.;Szabo, L.J.;Vaconcelos, A.C.;Cashmore, A.R.
  4. Curr. Opin. Plant Biol. v.2 Protein import into chloroplasts Keegstra, K.;Froehlich, J.E.
  5. J. Biol. Chem. v.274 Tic22 is targeted to the intermembrane space of chloroplasts by a novel pathway Kouranow, A.;Wang, H.;Schnell, D.J.
  6. J. Cell Biol. v.143 Tic20 and Tic22 are new components of the protein import apparatus at the chloroplast inner envelope membrane Kouranov, A.;Chen, X.J.;Fuks, B.;Schnell, D.J.
  7. Plant Cell v.8 Protein targeting and integration signal for the chloroplastic outer envelope membrane Li, H.M.;Chen, L.J.
  8. Plant Cell v.3 Targeting of proteins to the outer envelope membrane uses a different pathway than transport into chloroplasts Li, H.M.;Moore, T.;Keegstra, K.
  9. Plant Cell v.12 14-3-3 proteins from a guidance complex with chloroplast precursor proteins in plants May, T.;Soll, J.
  10. J. Biol. Chem. v.271 A protein import receptor of chloroplast is inserted into the outer envelope membrane by a novel pathway Muckel, E.;Soll, J.
  11. Plant Physiol v.123 Molecular cloning and targeting of a fibrillarin homolog from Arabidopsis Pih, K.T.;Yi, M.J.;Liang, Y.S.;Shin, B.J.;Cho, M.J.;Hwang, I.;Son, D.
  12. Plant J. v.13 Expression of a dominant negative from of cpSRP54 inhibits chloroplast biogenesis in Arabidopsis Pilgrim, M.L.;van Wijk, K.J.;Parry, D.H.;Sy, D.A.;Hoffman, N.E.
  13. J. Cell Biol. v.148 Toc64, a new component of the protein translocon of chloroplasts Sohrt, K.;Soll, J.
  14. J. Biol. Chem. v.274 Tic40, a new 'old' subunit of the chloroplast protein import translocon Stahl, T.;Glockmann, C.;Soll, J.;Heins, L.
  15. Proc. Natl. Acad. Sci. U S A. v.97 Toc34 is a preprotein receptor regulated by GTP and phosphorylation Sveshnikova, N.;Soll J.;Schleiff, E.