Crystal structure of pea Toc34, a novel GTPase of the chloroplast protein translocon
| Autor: | Chwan-Deng Hsiao, Hsou-min Li, Farhad Forouhar, Chinpan Chen, Sen Kao, Yuh-Ju Sun, Shuh-Long Tu, Chia-Cheng Chou, Hui-Lin Shr, Yi-Hong Yeh |
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| Rok vydání: | 2001 |
| Předmět: |
Toc complex
Models Molecular Chloroplasts GTPase-activating protein Protein Conformation Amino Acid Motifs Molecular Sequence Data Biology Arginine Crystallography X-Ray Biochemistry Guanosine Diphosphate GTP Phosphohydrolases Residue (chemistry) Cytosol Structural Biology Genetics Magnesium Amino Acid Sequence Integral membrane protein Plant Proteins Binding Sites GTPase-Activating Proteins Peas Membrane Proteins Chloroplast outer membrane Translocon Transport protein Cytosolic part Protein Transport Mutation Biophysics Chromatography Gel Guanosine Triphosphate Dimerization Sequence Alignment Protein Binding |
| Zdroj: | Nature structural biology. 9(2) |
| ISSN: | 1072-8368 |
| Popis: | 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 A 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 protein (GAP). However, gel filtration experiments revealed that dimeric and monomeric forms of Toc34 coexisted in phosphate saline buffer solution at pH 7.2. Mutation of Arg 128, an essential residue for dimerization, to an Ala residue led to the formation of an exclusively monomeric species whose GTPase activity is significantly reduced compared to that of wild type Toc34. These results, together with a number of structural features unique to Toc34, suggest that each monomer acts as a GAP on the other interacting monomer. |
| Databáze: | OpenAIRE |
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