Direct evidence for the size and conformational variability of the pyruvate dehydrogenase complex revealed by three-dimensional electron microscopy. The 'breathing' core and its functional relationship to protein dynamics
| Autor: | Z H, Zhou, W, Liao, R H, Cheng, J E, Lawson, D B, McCarthy, L J, Reed, J K, Stoops |
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| Rok vydání: | 2001 |
| Předmět: |
Geobacillus stearothermophilus
Models Molecular Microscopy Electron Protein Subunits Binding Sites Saccharomyces cerevisiae Proteins Acetyltransferases Protein Conformation Image Processing Computer-Assisted Pyruvate Dehydrogenase Complex Saccharomyces cerevisiae Dihydrolipoyllysine-Residue Acetyltransferase Protein Structure Secondary |
| Zdroj: | The Journal of biological chemistry. 276(24) |
| ISSN: | 0021-9258 |
| Popis: | Structural studies by three-dimensional electron microscopy of the Saccharomyces cerevisiae truncated dihydrolipoamide acetyltransferase (tE(2)) component of the pyruvate dehydrogenase complex reveal an extraordinary example of protein dynamics. The tE(2) forms a 60-subunit core with the morphology of a pentagonal dodecahedron and consists of 20 cone-shaped trimers interconnected by 30 bridges. Frozen-hydrated and stained molecules of tE(2) in the same field vary in size approximately 20%. Analyses of the data show that the size distribution is bell-shaped, and there is an approximately 40-A difference in the diameter of the smallest and largest structures that corresponds to approximately 14 A of variation in the length of the bridge between interconnected trimers. Companion studies of mature E(2) show that the complex of the intact subunit exhibits a similar size variation. The x-ray structure of Bacillus stearothermophilus tE(2) shows that there is an approximately 10-A gap between adjacent trimers and that the trimers are interconnected by the potentially flexible C-terminal ends of two adjacent subunits. We propose that this springlike feature is involved in a thermally driven expansion and contraction of the core and, since it appears to be a common feature in the phylogeny of pyruvate dehydrogenase complexes, protein dynamics is an integral component of the function of these multienzyme complexes. |
| Databáze: | OpenAIRE |
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