Gene Symbol: TOC33
Description: translocon at the outer envelope membrane of chloroplasts 33
Alias: ATTOC33, PLASTID PROTEIN IMPORT 1, PPI1, T6A9.32, translocon at the outer envelope membrane of chloroplasts 33, translocon at the outer envelope membrane of chloroplasts 33
Species: thale cress
Products:     TOC33

Top Publications

  1. Smith M, Hiltbrunner A, Kessler F, Schnell D. 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. 2002;159:833-43 pubmed
    ..Targeting is mediated by direct binding between the GTPase domain of atToc159 and the homologous GTPase domain of atToc33, the Arabidopsis Toc33/34 orthologue...
  2. Bae W, Lee Y, Kim D, Lee J, Kim S, Sohn E, et al. AKR2A-mediated import of chloroplast outer membrane proteins is essential for chloroplast biogenesis. Nat Cell Biol. 2008;10:220-7 pubmed publisher
    ..Thus, AKR2A functions as a cytosolic mediator for sorting and targeting of nascent chloroplast OEM proteins to the chloroplast. ..
  3. Gutensohn M, Schulz B, Nicolay P, Flügge U. Functional analysis of the two Arabidopsis homologues of Toc34, a component of the chloroplast protein import apparatus. Plant J. 2000;23:771-83 pubmed
    Two Arabidopsis Toc34 homologues, atToc34 and atToc33, components of the chloroplast protein import machinery located in the outer envelope membrane, were recently isolated...
  4. Jarvis P, Chen L, Li H, Peto C, Fankhauser C, Chory J. An Arabidopsis mutant defective in the plastid general protein import apparatus. Science. 1998;282:100-3 pubmed
    ..mutant lacking a new component of the import machinery [translocon at the outer envelope membrane of chloroplasts (Toc33), a 33-kilodalton protein] has been isolated...
  5. Bionda T, Koenig P, Oreb M, Tews I, Schleiff E. pH sensitivity of the GTPase Toc33 as a regulatory circuit for protein translocation into chloroplasts. Plant Cell Physiol. 2008;49:1917-21 pubmed publisher
    ..We show that the hydrolytic activity of the GTPase Toc33 is pH insensitive in the homodimeric conformation but has a bell-shaped pH optimum in the monomeric conformation...
  6. 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. 2003;278:44289-97 pubmed
    ..In the present study, we used the Arabidopsis thaliana orthologs of Toc159 and Toc34, atToc159 and atToc33, respectively, to investigate the requirements for assembly of the trimeric Toc complex...
  7. Koenig P, Oreb M, Höfle A, Kaltofen S, Rippe K, Sinning I, et al. The GTPase cycle of the chloroplast import receptors Toc33/Toc34: implications from monomeric and dimeric structures. Structure. 2008;16:585-96 pubmed publisher
    Transport of precursor proteins across chloroplast membranes involves the GTPases Toc33/34 and Toc159 at the outer chloroplast envelope...
  8. Weibel P, Hiltbrunner A, Brand L, Kessler F. Dimerization of Toc-GTPases at the chloroplast protein import machinery. J Biol Chem. 2003;278:37321-9 pubmed
    ..of chloroplast precursor proteins is controlled by the coordinate action of two homologous GTPases, Toc159 and Toc33, located at the cytosol-outer membrane interface...
  9. Ling Q, Huang W, Baldwin A, Jarvis P. Chloroplast biogenesis is regulated by direct action of the ubiquitin-proteasome system. Science. 2012;338:655-9 pubmed publisher
    ..Thus, the ubiquitin-proteasome system acts on plastids to control their development. ..

More Information


  1. Aronsson H, Combe J, Jarvis P. Unusual nucleotide-binding properties of the chloroplast protein import receptor, atToc33. FEBS Lett. 2003;544:79-85 pubmed
    Arabidopsis Toc33 (atToc33) is a GTP-binding protein of the chloroplast outer envelope membrane. We studied its nucleotide-binding properties in vitro, and found that it binds GTP, GDP and XTP, with similar efficiencies, but not ATP...
  2. Bauer J, Hiltbrunner A, Weibel P, Vidi P, Alvarez Huerta M, Smith M, et al. Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membrane. J Cell Biol. 2002;159:845-54 pubmed
    Two homologous GTP-binding proteins, atToc33 and atToc159, control access of cytosolic precursor proteins to the chloroplast...
  3. Aronsson H, Combe J, Patel R, Agne B, Martin M, Kessler F, et al. Nucleotide binding and dimerization at the chloroplast pre-protein import receptor, atToc33, are not essential in vivo but do increase import efficiency. Plant J. 2010;63:297-311 pubmed publisher
    ..It is a GTPase with motifs characteristic of such proteins, and its loss in the plastid protein import 1 (ppi1) mutant interferes with the import of photosynthesis-related pre-proteins, causing a chlorotic ..
  4. Koenig P, Oreb M, Rippe K, Muhle Goll C, Sinning I, Schleiff E, et al. On the significance of Toc-GTPase homodimers. J Biol Chem. 2008;283:23104-12 pubmed publisher
    ..overall fold and nucleotide binding, as seen in the monomeric x-ray crystallographic structure of the Arabidopsis Toc33 arginine-alanine replacement variant at 2.0A...
  5. Oreb M, Höfle A, Koenig P, Sommer M, Sinning I, Wang F, et al. Substrate binding disrupts dimerization and induces nucleotide exchange of the chloroplast GTPase Toc33. Biochem J. 2011;436:313-9 pubmed publisher
    ..of chloroplasts/inner envelope membrane of chloroplasts)] is controlled by two homologous receptor GTPases, Toc33 and Toc159, whose reversible dimerization is proposed to regulate translocation of incoming proteins in a GTP-..
  6. Reinbothe S, Pollmann S, Springer A, James R, Tichtinsky G, Reinbothe C. A role of Toc33 in the protochlorophyllide-dependent plastid import pathway of NADPH:protochlorophyllide oxidoreductase (POR) A. Plant J. 2005;42:1-12 pubmed
    ..outer envelope protein Oep16 (named Ptc16) and a 33-kDa protein (Ptc33) related to the GTP-binding proteins Toc33 and Toc34 of Arabidopsis...
  7. Rahim G, Bischof S, Kessler F, Agne B. In vivo interaction between atToc33 and atToc159 GTP-binding domains demonstrated in a plant split-ubiquitin system. J Exp Bot. 2009;60:257-67 pubmed publisher
    The GTPases atToc33 and atToc159 are pre-protein receptor components of the translocon complex at the outer chloroplast membrane in Arabidopsis...
  8. Agne B, Infanger S, Wang F, Hofstetter V, Rahim G, Martin M, et al. A toc159 import receptor mutant, defective in hydrolysis of GTP, supports preprotein import into chloroplasts. J Biol Chem. 2009;284:8670-9 pubmed publisher
    ..The data also indicate that preprotein import requires at least one additional GTPase other than Toc159. ..
  9. Dhanoa P, Richardson L, Smith M, Gidda S, Henderson M, Andrews D, et al. Distinct pathways mediate the sorting of tail-anchored proteins to the plastid outer envelope. PLoS ONE. 2010;5:e10098 pubmed publisher
    ..TA proteins, including the 33-kDa and 34-kDa GTPases of the translocon at the outer envelope of chloroplasts (Toc33 and Toc34) and a novel 9-kDa protein of unknown function that we define here as an outer envelope TA protein (OEP9)..
  10. Aronsson H, Jarvis P. Dimerization of TOC receptor GTPases and its implementation for the control of protein import into chloroplasts. Biochem J. 2011;436:e1-2 pubmed publisher
    ..of the TOC (translocon at the outer envelope membrane of chloroplasts) complex are the receptor proteins Toc33 and Toc159...
  11. Aronsson H, Combe J, Patel R, Jarvis P. In vivo assessment of the significance of phosphorylation of the Arabidopsis chloroplast protein import receptor, atToc33. FEBS Lett. 2006;580:649-55 pubmed
    b>atToc33 is a transit peptide receptor of the chloroplast outer envelope membrane, and possesses GTPase activity...
  12. Lee J, Wang F, Schnell D. Toc receptor dimerization participates in the initiation of membrane translocation during protein import into chloroplasts. J Biol Chem. 2009;284:31130-41 pubmed publisher
  13. Inaba T, Alvarez Huerta M, Li M, Bauer J, Ewers C, Kessler F, et al. Arabidopsis tic110 is essential for the assembly and function of the protein import machinery of plastids. Plant Cell. 2005;17:1482-96 pubmed
    ..Together, these data suggest that Tic110 plays a general role in the import of nuclear-encoded preproteins as a common component of Tic complexes. ..
  14. von Loeffelholz O, Kriechbaumer V, Ewan R, Jonczyk R, Lehmann S, Young J, et al. OEP61 is a chaperone receptor at the plastid outer envelope. Biochem J. 2011;438:143-53 pubmed publisher
    ..We therefore propose that OEP61 is a novel chaperone receptor at the chloroplast outer envelope, mediating Hsp70-dependent protein targeting to chloroplasts. ..
  15. Oreb M, Zoryan M, Vojta A, Maier U, Eichacker L, Schleiff E. Phospho-mimicry mutant of atToc33 affects early development of Arabidopsis thaliana. FEBS Lett. 2007;581:5945-51 pubmed
    The precursor protein receptor at the chloroplast outer membrane atToc33 is a GTPase, which can be inactivated by phosphorylation in vitro, being arrested in the GDP loaded state...
  16. Reddick L, Vaughn M, Wright S, Campbell I, Bruce B. In vitro comparative kinetic analysis of the chloroplast Toc GTPases. J Biol Chem. 2007;282:11410-26 pubmed
    ..Here we present the first systematic kinetic characterization of four Toc GTPases (cytosolic domains of atToc33, atToc34, psToc34, and the GTPase domain of atToc159) to permit their direct comparison...
  17. Sommer M, Rudolf M, Tillmann B, Tripp J, Sommer M, Schleiff E. Toc33 and Toc64-III cooperate in precursor protein import into the chloroplasts of Arabidopsis thaliana. Plant Cell Environ. 2013;36:970-83 pubmed publisher
    ..phenotype, which is distinct from the phenotype of ppi1, the previously described mutant of the TOC34 homolog TOC33. Furthermore, chloroplast import of the model precursor proteins pOE33 and pSSU into chloroplasts is reduced in ..