Membrane Proteins and the Secretory Pathway Flashcards Preview

Foundations 1 > Membrane Proteins and the Secretory Pathway > Flashcards

Flashcards in Membrane Proteins and the Secretory Pathway Deck (46):
1

four types of membrane proteins

transmembrane, monolayer-associated, lipid-linked, protein-attached

2

Type I topology

single pass protein anchroed to the lipid membrane with a stop transfer anchro sequence, have their N-terminus targeted to the ER lumen

3

Type II topology

single pass protein anchored with a single-anchor sequence and hte carboxyl terminus in the ER lumen

4

Type III topology

single pass protein with a signal-anchor sequence and the amino terminus in the ER lumen

5

Type IV topology

multi-pass protein, amino terminus on either side

6

glycosylphosphatidylinositol (GPI) anchor

modified lipid in cell membrane that cells adhere to

some type I proteins exchange their carboxyl terminal transmembrane segment for a GPI anchor

7

Describe the directions of vesicular traffic in cells.

8

protein transport into ER

signal recognition particle (SRP) recognizes signal sequence and brings it to receptor in the ER membrane

protein goes through channel, and signal is eventually cleaved by a signal peptidase

9

What are some different ways to orient proteins based on signal sequence?

10

N-linked glycosylation

the process of adding sugar molecules onto all proteins in the ER membrane, same sugars

important for protein stability

11

BiP

one of many ATP-dependent chaperones that assist folding as the protien emerges from the translocon

12

Calnexin

calcium binding protein that monitors that folding of glycoproteins

binds to oligosaccharides and "senses" when the protein is correctly folded

13

mannosidases

trim mannose residues from the oligosaccharide, function similarly to calnexin to ensure proper folding

14

protein disulfide isomerases (PDIs)

catalyze formation of disulfide bonds

15

ERP57

chaperone protein that works with calnexin to ensure proper folding of proteins using the trimming of the oligosaccharides as a guide

16

SEL1

protein in the ER that pushes improperly folded proteins out as a single chain, which is then polyubiquitinylated and degraded

17

PERK

protein kinase that phosphorylates eIF2alpha, which blocks translation

ATF4 can escape the transtion block so it goes to the nucleus and activates a stress response

18

ATF6

released from the ER membrane by high levels of BiP, and goes through the golgi to get cleaved and become a transcription factor to activate stress genes

19

IRE1

BiP interaction activates a unique splicing mechanism, causes intron mechanism for XBP1 to be inactivated, creating a transcription factor to activate a stress response

also responsible for triggering autophagy or apoptosis through activation of Jun Kinase

20

unfolded protein response

a collection of several mechanisms the cell can undergo to deal with unfolded proteins

uses BiP as a sensor

21

ER-associated degradation (ERAD)

a process of degradation that proteins undergo if proteins cannot fold properly or take too long to fold in the ER, uses SEL1 to unfold proteins and mark for degradation

22

functions of the cis golgi network

sorting, phosphorylation of oligosaccharides on lysosomal proteins

23

functions of the cis cisterna of golgi

removal of mannose

24

function of mdial cisterna of golgi

removal of mannose and addition of N-acetyl-glucose (GlcNac)

25

trans cisterna

addition of galactose and NANA

26

trans golgi network

sulfation of tyrosines and carbohydrates, prepare for vesicular transport

27

Describe the vesicular transport from the Golgi.

28

packaging of cargo in the Golgi

need coat complex II (COPII)

recruitment of cargo proteins and coat machinery

formation of vesicle that pinches off

29

vesicle compartment topology

lumenal aspect of the ER correlates to the outside of the cell once the transport completes

30

recycling of components

uses coat complex COPI and peptide sequences often have a KDEL motif that directs ER proteins form the GOlgi to recyling

31

mannose-6-phosphate receptors

integral membrane proteins that bind lumenal lysosomal hydrolases, causes formation of clathrin coated vesicles

marked for transport to early or late endosomes, which become lysosomes

32

exosomes

small vesicles released from the plasma membrane

have roles in coagulation, intercellular signaling, and waste management

generated in multivesicular endosomes

can possible shuttle ncRNAs to other cells for signaling and regulation

33

three types of endocytosis

phagocytosis, pinocytosis, receptor-mediated endocytosis

34

pinocytosis

ingestion of small bits of the plasma membrane with extracellular fluid

small vesicles c alled caveolae

35

phagocytosis

ingestion of large parthicles and delivery to lysosomes

requires the actin cytoskeleton

36

receptor-mediated endocytosis

responsible for uptake of essential nutrients such as iron and cholesterol

used to recycle and down-regulate receptors

uses clathrin coat and adaptin molecules along with the specific receptors

37

endosomes

come from endocytosed vesicles that fuse with each other, early and late endosomes, eventually becomes lysosomes and contents are degraded

38

two types of autophagy

microautophagy and macroautophagy

operates to recycle cellular components, active under startvation conditions

39

microautophagy

occurs by the capture of small volumes of cytoplasm by invagination of the membranes in multivesicular bodies and lysosomes

cytoplasmic components are hydrolyzed within the lysosomes

40

macroautophagy

involves the engulfment of large volumes of cytoplasm including glycogen granules, ribosomes, and organelles

41

autophagic vacuole

forms when flattened sheets of membranes derived from the smooth ER coalesce to form a double membrane vesicle

fusion with lysosomes forms an autolysosome, where engulfed contents are degraded

42

two types of secretion

constitutive secretion - simply move materials out of the cell in regular intervals, both soluble and membrane associated proteins

regulated membrane fusion - take secretory vesicles and accumulate them near the plasma membrane, only allow them to fuse with the plasma membrane when stimulated with a signal, electrical activity, etc.

43

three fates of internalized receptors

recycled, degraded, transcytosed

44

Descrube the sorting of proteins from the trans golgi network to the lysosome.

indirect and direct pathways

indirect goes from golgi to membrane, which can then be engulfed and degraded

direct goes to late endosome and then lysosome or goes directly to lysosome

45

Describe the composition of the lysosome.

46

sorting of plasma membrane proteins in polarized cells

direct sorting - goes from Golgi to the right surface of the cell

indirect sorting - goes from golgi to basolateral surface and then sorted from there through early endosomes