Degradation

The lifespan of proteins varies depending on their kind. Some proteins are degraded after a few minutes of production; others remain for years. Misfolded proteins are degraded at once to prevent them from causing damage due to their instability and dysfunctional nature. The cell may degrade or recycle them through protein turnover. Proteins may be degraded in proteasomes, i.e. cytoplasmic complexes that digest worn-out or misfolded proteins tagged with ubiquitin. In eukaryotes, another site of protein degradation is the lysosome. Lysosomes contain proteases that digest endocytosed proteins.