How long can a protein exist before it is degraded or replaced in a cell?

How long can a protein exist before it is degraded or replaced in a cell?

• A. Always a few hours
• B. Typically days to weeks
• C. As little as 5 minutes or as long as 20–30 days
• D. Never leaves the cell

Answer: (C)

Proteins have finite lifespans in cells; they are continually built up and broken down in a process called protein turnover. How long a protein lasts before degradation or replacement depends on its function and regulation. Some proteins are rapidly turned over and exist for only minutes, while others are quite stable and can persist for days or even weeks. The range from as little as about 5 minutes to 20–30 days captures this wide variability and is the best description of how long a protein can persist. Degradation is mediated mainly by systems like the ubiquitin-proteasome pathway for short-lived proteins and lysosomal pathways for others, which explains why some proteins cycle quickly while others remain longer. Statements claiming a fixed short duration or that proteins never leave the cell don’t fit the dynamic nature of protein turnover.

Proteins have finite lifespans in cells; they are continually built up and broken down in a process called protein turnover. How long a protein lasts before degradation or replacement depends on its function and regulation. Some proteins are rapidly turned over and exist for only minutes, while others are quite stable and can persist for days or even weeks. The range from as little as about 5 minutes to 20–30 days captures this wide variability and is the best description of how long a protein can persist. Degradation is mediated mainly by systems like the ubiquitin-proteasome pathway for short-lived proteins and lysosomal pathways for others, which explains why some proteins cycle quickly while others remain longer. Statements claiming a fixed short duration or that proteins never leave the cell don’t fit the dynamic nature of protein turnover.