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From Proteopedia
Dimerization is important for the GTPase activity of chloroplast translocon components atToc33 and psToc159
Structural highlights
FunctionTOC33_ARATH GTPase involved in protein precursor import into chloroplasts. Seems to recognize chloroplast-destined precursor proteins and regulate their presentation to the translocation channel through GTP hydrolysis. Binds GTP, GDP, XTP, but not ATP. Probably specialized in the import of nuclear encoded photosynthetic preproteins from the cytoplasm to the chloroplast, especially during early development stages.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedArabidopsis Toc33 (atToc33) is a GTPase and a member of the Toc (translocon at the outer-envelope membrane of chloroplasts) complex that associates with precursor proteins during protein import into chloroplasts. By inference from the crystal structure of psToc34, a homologue in pea, the arginine at residue 130 (Arg(130)) has been implicated in the formation of the atToc33 dimer and in intermolecular GTPase activation within the dimer. Here we report the crystal structure at 3.2-A resolution of an atToc33 mutant, atToc33(R130A), in which Arg(130) was mutated to alanine. Both in solution and in crystals, atToc33(R130A) was present in its monomeric form. In contrast, both wild-type atToc33 and another pea Toc GTPase homologue, pea Toc159 (psToc159), were able to form dimers in solution. Dimeric atToc33 and psToc159 had significantly higher GTPase activity than monomeric atToc33, psToc159, and atToc33(R130A). Molecular modeling using the structures of psToc34 and atToc33(R130A) suggests that, in an architectural dimer of atToc33, Arg(130) from one monomer interacts with the beta-phosphate of GDP and several other amino acids of the other monomer. These results indicate that Arg(130) is critical for dimer formation, which is itself important for GTPase activity. Activation of GTPase activity by dimer formation is likely to be a critical regulatory step in protein import into chloroplasts. Dimerization is important for the GTPase activity of chloroplast translocon components atToc33 and psToc159.,Yeh YH, Kesavulu MM, Li HM, Wu SZ, Sun YJ, Konozy EH, Hsiao CD J Biol Chem. 2007 May 4;282(18):13845-53. Epub 2007 Mar 1. PMID:17337454[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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Categories: Arabidopsis thaliana | Large Structures | Hsiao C-D | Kesavulu MM | Konozy EH | Li H-M | Sun Y-J | Wu S-Z | Yeh Y-H
