Skip to main content
Log in

Toc GTPases

  • Published:
Journal of Biomedical Science

Abstract

Chloroplasts import more than 90% of their protein constituents from the cytosol. The import is mediated by translocon complexes located in the chloroplast envelope and the stroma. This review focuses on the two GTPases in the Toc (translocon at the outer envelope membrane of chloroplasts) complex. Hypotheses are presented about gating across the outer membrane and the possible functional states of the GTPases.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others

References

  1. Soll J., Schleiff E., Protein import into chloroplasts. Nat. Rev. Mol. Cell Biol. 5: 198–208, 2004

    Article  PubMed  CAS  Google Scholar 

  2. Kessler F., Schnell D.J., The function and diversity of plastid protein import pathways: a multilane GTPase highway into plastids. Traffic 7: 248–257, 2006

    Article  PubMed  CAS  Google Scholar 

  3. Chou M.-L., Chu C.-C., Chen L.-J., Akita M., Li H.-m., Stimulation of transit-peptide release and ATP hydrolysis by a cochaperone during protein import into chloroplasts. J. Cell Biol. 175: 893–900, 2006

    Article  PubMed  CAS  Google Scholar 

  4. Schleiff E., Soll J., Küchler M., Kühlbrandt W., Harrer R., Characterization of the translocon of the outer envelope of chloroplasts. J. Cell Biol. 160: 541–551, 2003

    Article  PubMed  CAS  Google Scholar 

  5. Hinnah S.C., Wagner R., Sveshnikova N., Harrer R., Soll J., The chloroplast protein import channel Toc75: pore properties and interaction with transit peptides. Biophy. J. 83: 899–911, 2002

    Article  CAS  Google Scholar 

  6. Young M.E., Keegstra K., Froehlich J.E., GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts. Plant Physiol. 121: 237–243, 1999

    Article  PubMed  CAS  Google Scholar 

  7. Kessler F., Blobel G., Patel H.A., Schnell D.J., Identification of two GTP-binding proteins in the chloroplast protein import machinery. Science 266: 1035–1039, 1994

    Article  PubMed  CAS  Google Scholar 

  8. Chen K., Chen X., Schnell D.J., Initial binding of preproteins involving the Toc159 receptor can be bypassed during protein import into chloroplasts. Plant Physiol. 122: 813–822, 2000

    Article  PubMed  CAS  Google Scholar 

  9. Schleiff E., Jelic M., Soll J., A GTP-driven motor moves proteins across the outer envelope of chloroplasts. Proc. Natl. Acad. Sci. USA 100: 4604–4609, 2003

    Article  PubMed  CAS  Google Scholar 

  10. Kessler F., Schnell D.J., Chloroplast protein import: solve the GTPase riddle for entry. Trends Cell Biol. 14: 334–338, 2004

    Article  PubMed  CAS  Google Scholar 

  11. Hiltbrunner A., Bauer J., Vidi P.-A., Infanger S., Weibel P., Hohwy M., Kessler F., Targeting of an abundant cytosolic form of the protein import receptor atToc159 to the outer chloroplast membrane. J. Cell Biol. 154: 309–316, 2001

    Article  PubMed  CAS  Google Scholar 

  12. Sun Y.-J., Forouhar F., Li H.-m., Tu S.-L., Yeh Y.-H., Kao S., Shr H.-L., Chou C.-C., Chen C., Hsiao C.-D., Crystal structure of pea Toc34, a novel GTPase of the chloroplast protein translocon. Nature Struc. Biol. 9: 95–100, 2002

    Article  CAS  Google Scholar 

  13. Weibel P., Hiltbrunner A., Brand L., Kessler F., Dimerization of Toc-GTPases at the chloroplast protein import machinery. J. Biol. Chem. 278: 37321–37329, 2003

    Article  PubMed  CAS  Google Scholar 

  14. Flügge U., Benz R., Pore-forming activity in the outer membrane of the chloroplast envelope. FEBS Lett. 169: 85–89, 1984

    Article  Google Scholar 

  15. Becker T., Jelic M., Vojta A., Radunz A., Soll J., Schleiff E., Preprotein recognition by the Toc complex. EMBO J 23: 520–530, 2004

    Article  PubMed  CAS  Google Scholar 

  16. Smith M.D., Hiltbrunner A., Kessler F., Schnell D.J., The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP. J. Cell Biol. 159: 833–843, 2002

    Article  PubMed  CAS  Google Scholar 

  17. Bauer J., Hiltbrunner A., Weibel P., Vidi P.-A., Alvarez-Huerta M., Smith M.D., Schnell D.J., Kessler F., Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membrane. J. Cell Biol. 159: 845–854, 2002

    Article  PubMed  CAS  Google Scholar 

  18. Wallas T., Smith M., Sanchez-Nieto S., Schnell D., The roles of Toc34 and Toc75 in targeting the Toc159 preprotein receptor to chloroplasts. J. Biol. Chem. 278: 44289–44297, 2003

    Article  PubMed  CAS  Google Scholar 

  19. Smith M., Rounds C., Wang F., Chen K., Afitlhile M., Schnell D., The cytoplasmic form of atToc159 is a selective transit peptide receptor for the import of nucleus-encoded chloroplast proteins. J. Cell Biol. 165: 323–334, 2004

    Article  PubMed  CAS  Google Scholar 

  20. Sveshnikova N., Soll J., Schleiff E., Toc34 is a preprotein receptor regulated by GTP and phosphorylation. Proc. Natl. Acad. Sci. USA 97: 4973–4978, 2000

    Article  PubMed  CAS  Google Scholar 

  21. Schleiff E., Soll J., Sveshnikova N., Tien R., Wright S., Dabney-Smith C., Subramanian C., Bruce B.D., Structural and guanosine triphosphate/diphosphate requirements for transit peptide recognition by the cytosolic domain of the chloroplast outer envelope receptor, Toc34. Biochemistry 41: 1934–1946, 2002

    Article  PubMed  CAS  Google Scholar 

  22. Jelic M., Soll J., Schleiff E., Two Toc34 homologues with different properties. Biochemistry 42: 5906–5916, 2003

    Article  PubMed  CAS  Google Scholar 

  23. Jelic M., Sveshnikova N., Motzkus M., Hörth P., Soll J., Schleiff E., The chloroplast import receptor Toc34 functions as preprotein-regulated GTPase. Biol. Chem. 383: 1875–1883, 2002

    Article  PubMed  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding authors

Correspondence to Hsou-min Li or Chwan-Deng Hsiao.

Additional information

This article is for the Special Issue of IMB 20th anniversary.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Li, Hm., Kesavulu, M.M., Su, PH. et al. Toc GTPases. J Biomed Sci 14, 505–508 (2007). https://doi.org/10.1007/s11373-007-9166-2

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11373-007-9166-2

Keywords

Navigation