Protein sorting II Flashcards
example of “professional secretory cell”
acinar cells of pancreas
what is TGN
trans golgi network
what does TGN do
sorts proteins to the lysosomes or secretory vesicle
trafficing of materials occurs by ____
vessicle transport
if a polypeptide only has a signal for import into the lumen of the ER, where will it go?
it will be secreted
his definition network of membranes involved in synthesis, secretion, whatever is ______
endomembrane
What are some functions of ER?
protein import, steroid hormone synthesis, calcium sequestering (in muscle), lipid synthesis, post-translational modifications of proteins
what are some types of protein modifications?
disulfide bonds, glycosylation (n-linked and o-linked), proline hydroxylation (important in collagen)
protein translocation into secretory system begins___
in rER
what is the signal peptide for ER
typically at N-terminus, about 16-30 aa long; 6-12 hydrophobic residues flanked by positively charged amino acids on
when the protein gets to the ER what happens to the signal peptide
cleaved proteolytically
GFP with a secretory peptide on it will go where?
it will follow the default pathway of secretion
how is ER protein transport from other types we have already studied
imported into ER while translation is occurring. Co-translational
what is the receptor for ER signaling peptide like?
cytosolic SRP (signal recognition particle) is a ribonucleoprotein complex; has a specific polypeptide called P54 that binds to signal peptide and tells the ribosome to stop translation
what energy is needed for import into ER?
you need GTP for the SRP complex, also you need energy for translation of protein.
what is the ER translocon? what does it associate with?
Sec 61 alpha; associates with ribosome so that protein goes across ER in unfolded form
characteristics of Sec 61?
channel gated by a peptide plug, has hydrophobic isoleucine alpha helices in the pore
(t/f) there is a set targeting polypeptide sequence for SRP to be recruited
No.
what does lumenal protein BiP do
it is a Hsc70 chaperone. It uses ATP hydrolysis to draw the protein into the ER lumen.
how is type 1 integral membrane protein unique?
the simplest;a single span; the Carboxy terminus is in the Cytosol
how is type 2 integral membrane protein unique?
its a single span with orientation the opposite of type 1
how is type 3 integral membrane protein unique?
it looks the same as type 1, but the mechanism is different
what serves as a stop-transfer anchor sequence in type 1 insertion into ER membrane?
the 20-25 hydrophobic alpha helix portion
T/F both type 2 and 3 integral membrane proteins have an N terminal signaling peptide
False. they have an internal signal anchor, and LACK the N-terminal one
T/F positively charged part of polypeptide always faces the cytosol
true. always.
Nearly all multi-pass proteins lack ______
a cleavable signal sequence
when the number of hydrophobic sequences is odd, what happens
N-terminus and carboxy terminus are on opposite sides of the plasma membrane.
do you have to rememberize the sugar tree?
yuuup.
all mature N-linked glycoproteins have the core of _____
(GlcNAc)2(Man)3
what is a dolicol
a carrier for sugar modifications; a lipid anchor
what are some famous glycoproteins?
blood group antigens; viruses (they use glycoproteins as cammo)
where and how do disulfide bonds happen
in rER with via protein disulfide isomerase (PDI)
unfolded protein response
Bip hops off of its linkage to Ire1 monomer to help the proteins fold. the Ire1 gets lonely and dimerizes. that thing splices a transcription factor
example of protein folding disorder
emphysema from bad alpha 1 antitrypsin. it doesn’ fold right, it can’t get secreted, so it accumulates and does bad stuff.
