2. Glycoprotein folding by calreticulin
Quality control in ER
The process involves BIP, other
chaperons, PDI, …
The sensor assesses the
extent of folding by
monitoring exposed
hydrophobic regions. If
none are found the GP
passes into the transitional
ER. =glucosyltransferase
Mannose residues are
removed
3. Unfolded protein response
Heat, chemical insult, viral infection
Bip’s roles:
Protein import
Protein folding
Inactivation of
signaling molecules
4. The smooth ER
3 main types of lipids:
Glycolipids
Cholestrol
Synthesis of phospholipids
Phospholipids
SER is abundant in
Steroid producing cells
liver (containing
detoxifying enzymes
inactivating lipid-soluble
compounds)
5. Translocation of
phospholipids across the
ER membrane
There are several families of
these enzymes, some of which
are specific for particular
phospholipids.
12. Protein glycosylation
o Processing of N-Linked oligosaccharides for proteins destined for secretion
or for the plasma membrane
GlycosyltransferaseGlycosidase
13. o Targeting of lysosomal proteins by phosphorylation of mannose residues
The recognition determinants that lead to mannose phosphorylation are signal patches
in contrast to linear signals.
This recognition depends on the three-dimensional conformation of the folded protein.
