What is extracellular matrix?
Specialized material outside of the cell
What are the two types of protein sorting?
1. Post-Translational Process
Fully synthesised in cytosol before sorting
Unfolded: mitochondria, plastids
Folded: nucleus, peroxisomes
2. Co-Translational Process
During translation you sort it
What are the three types of Protein Sorting mechanisms?
Gated Transport
Transmembrane Transport
Vesicular Transport
What is Gated Transport?
Proteins moving between cytosol and nucleus
For example the selective transport of macromolecules and free diffusion of small molecules
How do proteins move into the nucleus?
Through a Nuclear Import Receptor. The nuclear import receptor binds to the nuclear import localization signal (NLS, rich in Arg and Lys specific)
How do proteins move out of the nucleus?
Through Nuclear Export Receptor, which Cargo proteins bind to using their Nuclear Export Signal (NES)
What is required for nuclear import and export?
Ran GTPase
How is GTPase regulated?
Ran-GAP (GTPase-activating protein)- stimulates GTP hydrolysis by Ran
Ran-GEF(Guanine nucleotide exchange factor)- Promotes the exchange of GDP for GTP
Where are Ran-GAP and Ran-GEF found in the nucleus and cytosol?
Ran-GAP is in the cytosol and Ran-GEF is in the nucleus
What are the concentrations of Ran-GTP in the nucleus and cytosol
High Ran-GTP in nucleus and low Ran-GTP in cytosol
How is Ran-GDP transported back to the nucleus?
Using a protein called NTF2 (Nuclear Transport Factor 2)
What are the steps for nuclear import?
1. Nuclear import receptor binds to cargo in cytosol
2. Receptor and cargo move into nucleus
3. Ran-GTP binding cause release of cargo
4. Now you have import receptor and Ran-GTP move into cytosol
5. Ran Binding Protein and Ran-GAP promote GTP hydrolysis and release of import receptor
What are the steps for nuclear export?
1. Nuclear export receptor binds to cargo and Ran-GTP
2. Receptor + Cargo + Ran-GTP move to cytosol
3. Ran Binding Protein and Ran-GAP promote GTP hydrolysis, release of cargo and receptor
4. Empty export receptor returns to nucleus
What is NFAT in its role in nuclear export and import?
high Ca2+ = nuclear import
low Ca2+= nuclear export
How do you sort proteins to the mitochondria?
Cytosolic chaperone proteins with protein that has signal sequence(N-terminal amphipathic a-helix) bind to import receptors of TOM and TIM23 complexes. Signal sequence is then cleaved
How do you sort proteins to the thylakoid?
Protein that has signal sequence(N-terminal amphipathic a-helix) bind to import receptors of TOC and TIC complexes. Signal sequence is then cleaved inside chloroplast and thylakoid signal sequence revealed goes into thylakoid.
How do you sort proteins to the peroxisome?
Receptor binds to 3 amino acid at C-terminus(SKL) and it attaches to docking protein. Docking protein moves it to translocator where it goes into peroxisome