[W3] Intracellular signalling Flashcards
(35 cards)
What is a protein targeting sequence?
A short peptide motif that directs a protein to a specific cellular compartment.
Name five types of protein targeting sequences.
- Signal sequence
- Transmembrane domain
- Organelle-specific uptake sequence
- Nuclear localisation sequence (NLS)
- Lipid/protein binding domains
What is the role of the signal sequence?
To direct newly synthesised proteins to the endoplasmic reticulum (ER) for secretion or membrane insertion.
What are transmembrane domains used for?
Anchoring proteins into lipid bilayers.
What is an NLS?
A nuclear localisation sequence that directs proteins into the nucleus.
What is the secretory pathway for proteins?
ER → Golgi apparatus → transport vesicles → plasma membrane or other destinations.
What role does the ER play in protein secretion?
It is the entry point where proteins are translocated and begin folding and modification.
What is the function of the Golgi apparatus in secretion?
It modifies, sorts, and packages proteins received from the ER.
What did the 2013 Nobel Prize in Physiology or Medicine recognize?
Discoveries in the mechanisms of vesicle trafficking by Schekman, Rothman, and Südhof.
What did Randy Schekman discover?
Genes that control vesicle trafficking in yeast (SEC genes).
What did James Rothman discover?
The SNARE protein complex that enables vesicles to fuse with target membranes.
What did Thomas Südhof discover?
How signals (like calcium) control the precise release of vesicle contents.
How did yeast mutants contribute to our understanding of secretion?
They showed how genetic mutations could block specific trafficking steps, helping identify key genes.
What are temperature-sensitive mutants?
Mutants that function normally at permissive temperatures but show defects at higher, non-permissive temperatures.
What are the two main intracellular trafficking pathways?
- Secretory pathway
- Endocytic pathway
What is the secretory pathway?
The transport route from the ER to the Golgi and then to the plasma membrane or lysosomes.
What is the endocytic pathway?
The route from the plasma membrane inward to endosomes and lysosomes.
What is a sorting signal in protein trafficking?
A sequence or structure that directs proteins to their correct location.
What does the KDEL signal do?
It retrieves ER-resident proteins that accidentally enter the Golgi, returning them to the ER.
What does ERGIC stand for?
ER-Golgi Intermediate Compartment.
What is the ERGIC?
A transient sorting station between the ER and the Golgi that handles quality control and sorting.
What are lysosomes and how are proteins targeted to them?
Degradative organelles; proteins are targeted using specific signals in the Golgi.
What defines the identity of an organelle membrane?
Specific combinations of coat proteins, Rab proteins, SNARE proteins, and membrane lipids.
What are coat proteins and what do they do?
Proteins like clathrin, COPI, and COPII that help form vesicles from donor membranes.
