Protein sorting II

Question 1

example of “professional secretory cell”

Answer 1

acinar cells of pancreas

Question 2

what is TGN

Answer 2

trans golgi network

Question 3

what does TGN do

Answer 3

sorts proteins to the lysosomes or secretory vesicle

Question 4

trafficing of materials occurs by ____

Answer 4

vessicle transport

Question 5

if a polypeptide only has a signal for import into the lumen of the ER, where will it go?

Answer 5

it will be secreted

Question 6

his definition network of membranes involved in synthesis, secretion, whatever is ______

Answer 6

endomembrane

Question 7

What are some functions of ER?

Answer 7

protein import, steroid hormone synthesis, calcium sequestering (in muscle), lipid synthesis, post-translational modifications of proteins

Question 8

what are some types of protein modifications?

Answer 8

disulfide bonds, glycosylation (n-linked and o-linked), proline hydroxylation (important in collagen)

Question 9

protein translocation into secretory system begins___

Answer 9

in rER

Question 10

what is the signal peptide for ER

Answer 10

typically at N-terminus, about 16-30 aa long; 6-12 hydrophobic residues flanked by positively charged amino acids on

Question 11

when the protein gets to the ER what happens to the signal peptide

Answer 11

cleaved proteolytically

Question 12

GFP with a secretory peptide on it will go where?

Answer 12

it will follow the default pathway of secretion

Question 13

how is ER protein transport from other types we have already studied

Answer 13

imported into ER while translation is occurring. Co-translational

Question 14

what is the receptor for ER signaling peptide like?

Answer 14

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

Question 15

what energy is needed for import into ER?

Answer 15

you need GTP for the SRP complex, also you need energy for translation of protein.

Question 16

what is the ER translocon? what does it associate with?

Answer 16

Sec 61 alpha; associates with ribosome so that protein goes across ER in unfolded form

Question 17

characteristics of Sec 61?

Answer 17

channel gated by a peptide plug, has hydrophobic isoleucine alpha helices in the pore

Question 18

(t/f) there is a set targeting polypeptide sequence for SRP to be recruited

Answer 18

No.

Question 19

what does lumenal protein BiP do

Answer 19

it is a Hsc70 chaperone. It uses ATP hydrolysis to draw the protein into the ER lumen.

Question 20

how is type 1 integral membrane protein unique?

Answer 20

the simplest;a single span; the Carboxy terminus is in the Cytosol

Question 21

how is type 2 integral membrane protein unique?

Answer 21

its a single span with orientation the opposite of type 1

Question 22

how is type 3 integral membrane protein unique?

Answer 22

it looks the same as type 1, but the mechanism is different

Question 23

what serves as a stop-transfer anchor sequence in type 1 insertion into ER membrane?

Answer 23

the 20-25 hydrophobic alpha helix portion

Question 24

T/F both type 2 and 3 integral membrane proteins have an N terminal signaling peptide

Answer 24

False. they have an internal signal anchor, and LACK the N-terminal one

Question 25

T/F positively charged part of polypeptide always faces the cytosol

Answer 25

true. always.

Question 26

Nearly all multi-pass proteins lack ______

Answer 26

a cleavable signal sequence

Question 27

when the number of hydrophobic sequences is odd, what happens

Answer 27

N-terminus and carboxy terminus are on opposite sides of the plasma membrane.

Question 28

do you have to rememberize the sugar tree?

Answer 28

yuuup.

Question 29

all mature N-linked glycoproteins have the core of _____

Answer 29

(GlcNAc)2(Man)3

Question 30

what is a dolicol

Answer 30

a carrier for sugar modifications; a lipid anchor

Question 31

what are some famous glycoproteins?

Answer 31

blood group antigens; viruses (they use glycoproteins as cammo)

Question 32

where and how do disulfide bonds happen

Answer 32

in rER with via protein disulfide isomerase (PDI)

Question 33

unfolded protein response

Answer 33

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

Question 34

example of protein folding disorder

Answer 34

emphysema from bad alpha 1 antitrypsin. it doesn’ fold right, it can’t get secreted, so it accumulates and does bad stuff.