Crystal structure of pea Toc34, a novel GTPase of the chloroplast protein translocon

@article{Sun2002CrystalSO,
  title={Crystal structure of pea Toc34, a novel GTPase of the chloroplast protein translocon},
  author={Yuh-Ju Sun and Farhad Forouhar and Hsou-min Li and S L Tu and Y.-H. Yeh and S. Kao and H. L. Shr and C. C. Chou and Chinpan Chen and Chwan-Deng Hsiao},
  journal={Nature Structural Biology},
  year={2002},
  volume={9},
  pages={95-100}
}
Toc34, a 34-kDa integral membrane protein, is a member of the Toc (translocon at the outer-envelope membrane of chloroplasts) complex, which associates with precursor proteins during protein transport across the chloroplast outer membrane. Here we report the 2.0 Å resolution crystal structure of the cytosolic part of pea Toc34 in complex with GDP and Mg2+. In the crystal, Toc34 molecules exist as dimers with features resembling those found in a small GTPase in complex with a GTPase activating… 
Structural components involved in plastid protein import.
TLDR
A crystal structure of the Toc64 tetratrico-peptide repeat (TPR) domain in complex with the C-terminal domains of the heat-shock proteins (Hsp) Hsp90 and Hsp70 is presented.
Dimerization of Toc-GTPases at the Chloroplast Protein Import Machinery*
TLDR
It is demonstrated that arginine 130 of Toc33 does not function as an Arginine-finger, and that Arg130 is involved in both homodimerization of TOC33 and in heterodimerized with the GTP-binding domain of Tc159.
Characterization of the translocon of the outer envelope of chloroplasts
TLDR
The protein translocon of the outer envelope of chloroplasts (Toc) consists of the core subunits Toc159, Toc75, and Toc34, and the core complex was purified to investigate the molecular structure.
On the Significance of Toc-GTPase Homodimers*
TLDR
This work probed the catalytic center with the transition state analogue GDP/AlFx using NMR and analytical ultracentrifugation, suggesting the residue can play a role in catalysis despite the non-GAP nature of the homodimer.
Protein Translocon at the Outer Envelope of Chloroplasts
TLDR
To understand the necessity of multiple isoforms of Toc components as found in Arabidopsis thaliana, expression analysis and tissue-specific localization were conducted and a technique for liposome size determination in a single spectrophotometric measurement was developed.
Dimerization of TOC receptor GTPases and its implementation for the control of protein import into chloroplasts.
TLDR
Evidence is presented that homodimerization of Toc33 prevents nucleotide exchange, thereby locking the receptor in the GDP-loaded state and preventing further activity, and which is discussed in the context of previous findings pertaining to TOC receptor dimerization and function.
In Vitro Comparative Kinetic Analysis of the Chloroplast Toc GTPases*
TLDR
The first systematic kinetic characterization of four Toc GTPases is presented, indicating that transit peptides function as GTPase-activating proteins and not guanine nucleotide exchange factors in modulating the activity of psToc34, and providing new insights of how the chloroplast protein import cycle may be regulated.
Dimerization Is Important for the GTPase Activity of Chloroplast Translocon Components atToc33 and psToc159*
TLDR
Molecular modeling suggests that, in an architectural dimer of atToc33, Arg130 from one monomer interacts with the β-phosphate of GDP and several other amino acids of the other monomer.
Toc Receptor Dimerization Participates in the Initiation of Membrane Translocation during Protein Import into Chloroplasts*
TLDR
It is shown that specific mutations that disrupted receptor dimerization in vitro reduced the rate of protein import in transgenic Arabidopsis compared with the wild type receptor, and support a hypothesis in which receptor-receptor interactions participate in the initiation of membrane translocation of chloroplast preproteins as part of the molecular mechanism of GTP-regulated protein import.
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TLDR
This study demonstrates that atToc159 and its pea orthologue exist in an abundant, previously unrecognized soluble form, and partition between cytosol-containing soluble fractions and the chloroplast outer membrane, and suggests that the function of the Toc complex involves switching of atTOC159 between a soluble and an integral membrane form.
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TLDR
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TLDR
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TLDR
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