Endocytosis and Protein Degradation Flashcards Preview

M2M Unit III > Endocytosis and Protein Degradation > Flashcards

Flashcards in Endocytosis and Protein Degradation Deck (14):
1

Routes for small volume endocytosis (2)

Phagocytosis: engulfing of material followed by delivery to lysosome.
Pinocytosis: small volume endocytosis mediated by ligand/receptor uptake via clathrin or caveolae.

2

Clathrin

Receptor binds cargo, R recognized by cytoplasmic adaptor, clathrin associates, dynamin pinches off vesicle.

3

Quality control in ER

30% of protein gets misfolded and degraded because they will otherwise aggregate
ER provides oxidation environment for folding and oligomeric assembly

4

Hsp 60 and Hsp 70

Hsp60: ATP-dependent, places protein in isolation chamber, "pulls" protein to have it "spring back" into correct conformation.
Hsp70 (BiP): Binds to hydrophobic regions of protein during folding

5

ERp57

thiol oxidoreductase, assists with disulphide bond formation. Associates with Calnexin and Calreticulin

6

Calnexin and Calreticulin

Calnexin (trasmembrane) and Calreticulin: ER proteins that bind glucose residues added to proteins in ER and promote interactions with folding proteins. Glucose cleaved with dissociation.

7

Glycosyl Transferase

Adds glucose to UGGT sequence of protein (marker for misfolding). Causes association with Calnexin/Calreticulin to promote folding assistance.

8

Proteasome targeting

Requires 4+ ubiquitin chain on lysine residue

9

Addition of Ubiquitin process

3 steps:
1. E1 (activation) adds Ubq to E2 protein
2. E2 (conjugation) carries Ubq and associates with E3
3. E3 (ligation) recognizes protein and transfers Ubq from E2 to lysine residue or other Ubq

10

Protein at Proteasome

ATP utilized to unfold protein. Protein is fed into antechamber of proteasome composed of alpha subunits.
Protein enters central chamber of beta subunits which cleave protein into 7-9 AA pieces.
No ATP is required for cleavage.

11

B1 subunits

caspase-like activity for acidic AAs

12

B2 subunits

trypsin-like activity for basic AAs

13

B3 subuints

chymotrypsin-like activity for hydrophobic AAs

14

Lysosome function

Degrades endocytosed material and some intracellular components via enzymes functioning at low pH within vesicle. Low pH achieved through proton pump.