Intermediate filament | Polypeptides | Expressed in |
---|---|---|
nuclear | lamins A, B and C | nuclear lamina |
epithelial | keratins | epithelial cells |
axonal | neurofilament proteins | neurons |
vimentin-like | vimentin | many mesenchymal cells |
desmin | muscle | |
glial fibrillary acidic protein (GFAP) | astrocytes, some Schwann cells |
Membrane type | Hepatocyte | Pancreatic exocrine cell |
---|---|---|
plasma membrane | 2% | 5% |
rough ER | 35% | 60% |
smooth ER | 16% | <1% |
Golgi apparatus | 7% | 10% |
mitochondrial innermembrane | 32% | 17% |
mitochondrial outermembrane | 7% | 4% |
nuclear membrane | 0.2% | 0.7% |
lysosomes, peroxisomes, endosomes, secretory vesicles | <2% | <4% |
Vesicle | Coat and adaptor proteins | Small G protein | Transport step |
---|---|---|---|
clathrin | clathrin heavy and light chains, AP2 | ARF | plasma membrane → endosome |
clathrin heavy and light chains, AP1 | ARF | Golgi → endosome | |
clathrin heavy and light chains, AP3 | ARF | Golgi → lysosome | |
COPI | COP α, β, β′, γ, δ, ε, ζ | ARF | Golgi → ER; between Golgi cisternae |
COPII | Sar1 | ER → Golgi |
Type of Rab | Cellular compartment |
---|---|
Rab1 | ER and Golgi network |
Rab2 | cis Golgi network |
Rab6 | medial and trans Golgi network |
Rab5A | clathrin-coated vesicles |
Rab5C and Rab4 | early endosomes |
Rab7 | late endosomes |
Rab8 | basolateral secretory vesicles |
Rab3 | synaptic and secretory vesicles |
Function of signal sequence | Example of signal sequence |
---|---|
import into nucleus | PPKKKRKV |
export from nucleus | LALKLAGLDI |
import into mitochondria | |
import into peroxisome | SKL-COO− |
import into ER | |
return to ER | KDEL-COO− |
Modification | Addition | Substrates | Membrane affinity, KD |
---|---|---|---|
farnesylation | post-translation | cytosolic proteins | 100 μmol l−1 |
geranylgeranylation | post-translation | cytosolic proteins | 2 μmol l−1 |
N-myristoylation | co-translation | nascentpolypeptide | 80 μmol l−1 |
palmitoylation | post-translation | membrane protein | 5 μmol l−1 |