Protein Targeting and Degradation
Start with the big picture
Protein targeting begins with intrinsic signal sequences that direct newly made proteins to specific cellular destinations. For ER-bound proteins, the signal recognition particle (SRP) recognizes a hydrophobic signal and brings the translating ribosome to the ER, where a translocon supports entry into the lumen or membrane. Other signals and transport systems guide proteins into the nucleus, mitochondria, and peroxisomes, while sorting tags and vesicle machinery support movement between compartments. Quality control removes misfolded proteins, including ER proteins returned to the cytosol through ER-associated degradation. Ubiquitin tagging can direct substrates to the proteasome. The lesson also places these mechanisms in clinical context, including disorders associated with disrupted targeting or trafficking.
What you'll learn
- Describe how signal sequences direct proteins to cellular destinations.
- Explain SRP-mediated ER targeting and translocation.
- Identify key sorting signals for ER retrieval and organelle import.
- Outline how ERAD and ubiquitin guide protein degradation.
- Relate targeting and trafficking defects to disease mechanisms.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
