Week 2 Protein Degradation Module Flashcards Preview

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Flashcards in Week 2 Protein Degradation Module Deck (24)
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1
Q

What is the functional difference between proteins with long life spans and proteins with relatively short lifespans?

A

Long lived proteins: may be involved with structure of the cell

Short lived proteins: need to respond quickly to change and are likely part of metabolic processes, cell signaling, or cell division

2
Q

Define Proteolysis

A

breakdown of proteins into peptide fragments and AAs

3
Q

Define proteases

A

the enzymes responsible for the breakdown of proteins

4
Q

What are the two pathways of protein degradation?

A

ubiquitin-proteasome pathway, lysosomal pathway

5
Q

describe the ubiquitin-proteasome pathway: general pathway? what does it degrade? does it require energy?

A

General pathway: proteins are marked with a chaing of ubiquitin molecules and then degraded by proteasomes

A selective process that degrades short-lived, damaged or misfolded proteins.

Requires ATP

6
Q

What enzymes are involved in ubiquination of proteins?

A

E1
E2
E3

7
Q

At what points is ATP needed for the ubiquitin-proteasome pathway?

A

ATP is needed to attach Ub to E1. and ATP is needed during the breakdown of proteins with proteasome

8
Q

Describe how the enzymes work in the ubiquitin-proteasome pathway

A

Ub attaches to E1 (ATP is hydrolyzed)–>E1-Ub transfers its Ub to E2–>E3 ligase transfers Ub to the target protein

9
Q

After a Ub tagged protein is degraded, what happens to attacehd Ub?

A

they are recylced

10
Q

What is the general structure of a proteasome?

A

contain an inner active site (protein degradation) and out protein binding sites.

11
Q

compare the relative number of different E3 and E1 enzymes?

A

the genome has >600 Ub E3 ligases and much fewer E1 enzymes.

12
Q

How do cytosolic proteins enter a lysosome?

A

Autophagy!

13
Q

What are the three types of Autophagy?

A

Macroautophagy, microautophagy, chaperone-mediated autophagy

14
Q

What types of things are consume with macroautophagy? (3)

A

proteins, protein aggregates, mitochondrium (organelles)

15
Q

Describe the process/steps of macroautophagy

A

an isolation membrane (double membrane) expands to engulf cytosolic cargo–>cargo is sequestered in autophagosome (closed isolation membrane)–>autophagosome fuses with lysosome and contents are degraded

16
Q

Describe the steps of microautophagy

A

lysosome invaginates and directly eats cytosolic components

17
Q

What is an autophagic tube? where is it seen?

A

the invagination of the lysosome seen during the process of microautophagy. Vesicles bud off the tube and into the lysosome.

18
Q

describe the selectivity of macroautophagy, microautophagy, and chaperone-mediated autophagy

A

micro and macro: can be random or selective.

Chaperone: highly selective

19
Q

what types of proteins are degraded by chaperone-mediated autophagy?

A

long-lived dispensable proteins (contrasts to Ub-mediated that degrades short lived)

20
Q

what motif targets proteins to chaperone-mediated autophagy?

A

KFEQR motif

21
Q

what are the steps of chaperone-mediated autophagy

A

Protein with KFEQR motif binds chaperone in cytosol–>chaperone targets protein to lysosomal membrane–>protein binds LAMP2A on surface of lysosomal membrane–>LAMP2A translocates protein into lysosomal lumen

22
Q

what induces autophagy?

A

cellular stress

23
Q

In general, what type of proteins are targeted by Ub-proteasome pathway and Autophagy? Selectivity?

A

Autophagy: long lived proteins and organelles (selective or non-selective)

Ub-Proteasome: short lived, damaged, or misfolded proteins. highly selective

24
Q

what is mTOR? what does it do? during cell stress?

A

mTOR is a master regulator that positively promotes cell growth and proliferation. in a healthy cell mTOR inhibits expression of autophagy related genes. Under cellular stress mTOR signaling is impaired and Atgs are upregulated

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