Overview of eukaryotic molecular chaperones in the cytosol

Published on October 1, 2007 Updated on July 8, 2020   39 min

Other Talks in the Category: Cell Biology

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Hi, my name is Jason Young from McGill University, and I'll be presenting an overview of eukaryotic molecular chaperones in the cytosol.
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Proteins are synthesized as linear polypeptides and must fold into complex three-dimensional structures to become functional. The folded functional conformation of a polypeptide is the native state. The basis of protein folding is that the native conformation of a polypeptide is determined by its primary amino acid sequence. Folding can start with a polypeptide in an extended unfolded state. As folding proceeds, the polypeptide becomes increasingly compact until it reaches the native state. Protein folding is driven by hydrophobic interactions, so that in the native state most hydrophobic amino acids are sequestered within the center of the protein, and hydrophilic amino acids around the surface. However, intermediates on the folding pathway can still have significant levels of exposed hydrophobic regions.
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Protein folding in the cell is complicated by a number of factors. The cellular environment is highly crowded with macromolecules which increases the rates and affinities of interactions within a polypeptide, but also between different polypeptides. Also, multiple unfolded proteins can be present at the same time inside a cell. This leads to an increased risk of protein aggregation, that is, non-productive interactions between unfolded polypeptides can cause the polypeptides to become insoluble. Plaques of insoluble polypeptides have been linked to a number of neurodegenerative diseases, including Alzheimer and Parkinson's syndromes. Furthermore, new polypeptides must be folded vectorially, as they are translated on ribosomes, while mature proteins that are denatured by stress conditions, such as heat shock, must be refolded. Therefore, cells have developed a system of molecular chaperones, which prevent protein aggregation and assist the folding of proteins.
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Overview of eukaryotic molecular chaperones in the cytosol

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