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inclusion bodies : ウィキペディア英語版 | inclusion bodies Inclusion bodies are nuclear or cytoplasmic aggregates of stainable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins. Inclusion bodies can also be hallmarks of genetic diseases, as in the case of Neuronal Inclusion bodies in disorders like Frontotemporal dementia and Parkinson's disease. Inclusion bodies contain very little host protein, ribosomal components or DNA/RNA fragments. They often almost exclusively contain the over expressed protein and aggregation in inclusion bodies has been reported to be reversible. It has been suggested that inclusion bodies are dynamic structures formed by an unbalanced equilibrium between aggregated and soluble proteins of ''E. coli''. There is a growing body of information indicating that formation of inclusion bodies occurs as a result of intracellular accumulation of partially folded expressed proteins which aggregate through non-covalent hydrophobic or ionic interactions or a combination of both. Inclusion bodies are dense electron-refractile particles of aggregated protein found in both the cytoplasmic and periplasmic spaces of ''E. coli'' during high-level expression of heterologous protein. It is generally assumed that high level expression of non-native protein (higher than 2% of cellular protein) and highly hydrophobic protein is more prone to lead to accumulation as inclusion bodies in ''E. coli''. In the case of proteins having disulfide bonds, formation of protein aggregates as inclusion bodies is anticipated since the reducing environment of bacterial cytosol inhibits the formation of disulfide bonds. The diameter of spherical bacterial inclusion bodies varies from 0.5–1.3 μm and the protein aggregates have either an amorphous or paracrystalline nature depending on the localization. Inclusion bodies have higher density (~1.3 mg ml−1) than many of the cellular components, and thus can be easily separated by high-speed centrifugation after cell disruption. Inclusion bodies despite being dense particles are highly hydrated and have a porous architecture. ==Composition== Inclusion bodies have a non-unit lipid membrane. Protein inclusion bodies are classically thought to contain misfolded protein. However, this has recently been contested, as green fluorescent protein will sometimes fluoresce in inclusion bodies, which indicates some resemblance of the native structure and researchers have recovered folded protein from inclusion bodies.〔Biochem Biophys Res Com 328(2005) 189-197〕〔Protein Eng 7(1994) 131-136〕〔Biochem Biophys Res Comm 312 (2003) 1383-1386〕
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