Lecture 9 Slides Flashcards Preview

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Flashcards in Lecture 9 Slides Deck (44):
1

Regulatory genes

Turn genes on and off

2

Four levels of regulation of gene expression

1. Transcription
2. Post transcription
3. Translation
4. Post translation

3

Three ways to regulate gene expression post transcription

RNA processing, eg splicing
Rna degradation
Rna transport, eg nuclear export

4

Half life of prokaryotic rna

Three minutes

5

Half life of eukaryotic rna

Minutes to hours

6

What does regulation depend on during translation

Whether or not ribosome can translate mRNA

7

Three ways to regulate gene expression post translation

Affect protein stability - some proteins denature easily
Some proteins are targeted for degradation
Modifications eg phosphorylation

8

Example of negative control in transcription

Repressing splicing so intron is not removed

9

Positive control example during transcription

Using an activator to make splicing happen

10

At what point in ponytail does mRNA start to degrade

When there are 25 or fewer adenines

11

Is mRNA decamped before degradation

Yes

12

In what direction does degradation happen

5' to 3'

13

What initiation factors initiate translation

EIF4G and eIF4E

14

What enzyme degrades poly A tail

Deadenylase

15

What is a translation repressor protein

A protein that blocks the start codon AUG

16

How can a newly synthesized protein fold?

1. Correctly folded without help
2. Correctly folded with help of a molecular chaperone
3. Incompletely folded and digested by the proteasome

17

What digests a protein that is incompletely folded

A proteosome

18

What kind of cells have proteosomes in the cytosol

Eukaryotes, archea, and some bacteria

19

What is Ubiquitin ligase

An enzyme that binds Ubiquitin

20

Where is Ubiquitin added to unwanted protein

To side chain, ends with N terminal. Add c terminal end of Ubiquitin.

21

Polyubiquitin

More than one Ubiquitin has been added to unwanted protein

22

What happens to unwanted protein once Ubiquitin has bound to it

It goes to a proteosome, where it is unfolded. Ubiquitin doesn't go in. Amino acids are recycled.

23

How many amino acids in Ubiquitin

72

24

How many lysine residues in Ubiquitin

Seven

25

What are the two subunits of Ubiquitin ligase? What is their function.

E2- Ubiquitin transferase
e3- recognizes target protein

26

What is E1 unit

It is the carrier of Ubiquitin

27

What does E1 do with the Ubiquitin it carries

It charges E2

28

What do proteosome target proteins have

PEST motif, which is phosphorylated

29

Destruction box

Amino acid sequence required for degradation

30

n-end rule

N-terminal amino acid of a protein determines its half life (likelihood of being degraded)

31

How is Ubiquitin ligase activated

Phosphorylation by protein kinase
Allosteric transition by ligand binding or protein subunit addition

32

How is a degradation signal activated

Phosphorylation by protein kinase
Unmasking by protein dissociation
Creation of destabilizing N-terminus

33

Density and molecular weight of proteosome

26s
2.5 MDa

34

Proteosome subunits

19s cap
20s cylinder (active site)

35

What is active site of proteosome

20s cylinder

36

What does unfolding and pulling of protein throufh cylinder require

ATP

37

How does target protein attach to proteosome

At unfoldase ring

38

Contents of cap of proteosome

Ubiquitin receptor
Unfoldase ring
Ubiquitin hydrolase (to release Ubiquitin)

39

Shape of unfoldase ring

Hexameric

40

Is inactivation by polyubiquination reversible

No

41

Cell life cycle phasesq

Interphase - G1, S phase, G2
M phase- mitosis and cytokinesis

42

What is cyclin

An enzyme whose concentration varies with stages of cell life cycle

43

When is cyclin concentration high? Low?

High in mitosis
Low during interphase

44

What are housekeeping genes

Constitutive genes - expressed all the time