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Section 4 > Protein Translation > Flashcards

Protein Translation Flashcards

1
Q

What are 6 features of mRNA. Draw it out in your mind.

A
  1. 5’ cap
  2. 5’ UTR
  3. AUG start codon
    (open reading frames)
  4. stop codon (UGA, UAA, UAG)
  5. 3’ UTR
  6. 3’ end poly a tail
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2
Q

Draw a tRNA molecule in your mind.

A

ok

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3
Q

How many bases make up a codon?

A

3

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4
Q

How many possible codon sequences are there?

A

64

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5
Q

What is inosine?

A

found in tRNA and can pair with A, C, or U

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6
Q

aminoacyl-tRNA synthesis?

A

tRNA + aminoacid + ATP = aminoacyl-tRNA + ADP + P

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7
Q

In what part of the cell does translation occur?

A

cytosol

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8
Q

Where do ribosomal subunits come from?

A

rRNA genes transcribed and processed in the nucleolus

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9
Q

After ribosomal subunits are synthesized in the cytosol, where do they go?

A

imported into the nucleus

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10
Q

Initiation of translation requires the correct assembly of what 3 things?

A
  1. small ribo subunit
  2. mRNA
  3. tRNA binds to the first codon, usually a methionine-tRNA met pairing with the AUG start codon
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11
Q

What are the 5 initiation steps of translation?

A
  1. eIF2a is activated by binding GTP
  2. binds initiator methionine-tRNA met to form the ternary complex
  3. binds small ribo subunit
  4. mRNA molecule binds –> pre-initiation complex
  5. large rib subunit binds –> initiation complex and eIF2a is hydrolyzed and released
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12
Q

What are the 5 steps of elongation?

A
  1. initiator methionine-tRNA binds to the P site of the ribosome
  2. a second aminoacyl-tRNA is placed into A site; requires EF-1/GTP
  3. peptidyl bond is formed between first and second AA
  4. ribosomes moves down one codon; assisted by EF-2;
  5. the mRNA-peptidyl-complex now occupies the P site and the A site is empty; uncharged tRNA leaves throuhg E site
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13
Q

Describe termination?

A
  1. stop codon enters A site
  2. eRF pairs with the stop codon
  3. erF-GTP is hydrolyzed and peptide is released from P site
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14
Q

What is eRF?

A

it binds to the stop codon with GTP and assisted the releasing of the peptide

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15
Q

What 4 types of antibiotics inhibit the growth of prokaryotes by selectively inhibiting prokaryotic ribosomes

A
  1. Streptomycin: binds to the small subunit and inhibits initiation
  2. Neomycin/Gentamicin: binds to ribosomes and causes mistranslation
  3. tetracyclin: blocks the A site and prevents tRNA form binding
  4. Chloramphenicol: prevents peptidyl bond formation
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16
Q

What are 2 ways to regulate translation?

A
  1. regulation by preventing the recognition of a start codon

2. regulating the activity of initiation factors

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17
Q

How is ef-2 inhibited (in general terms.. nothing specific)

A

phosphorylation

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18
Q

Secretion of protein steps (4)

A
  1. signal sequence emerges and SRP binds the signal and complex moves to ER
  2. SRP docking protein transfers the ribosome to the translocon
  3. SRP dissociates and translation continues and peptide is threaded into the ER
  4. signal peptidase cleaves the signal peptide
19
Q

What is the unfolded protein response?

A
  1. decrease in translation
  2. increase in chaperone proteins
  3. apoptosis
20
Q

Why is glycosylation important (2 reasons)

A
  1. changes the physical properties of the protein by increasing solubility, stability, and size
  2. carbs prob recognition sites (important for development or immune defense)
21
Q

Where does glycosylation of proteins begin? Where does it continue?

A

In the ER.. then in the mitochondria

22
Q

The unfolded protein response occurs in response to what 2 things?

A

starvation and cholesterol overload

23
Q

What are the steps of N-linked glycosylation?

A
  1. 2 GlcNACs from UDP-GlcNAc –> Dolichol P
  2. a mannosyltransferase transfers a mannose from UDP-mannose to the 2 GlcNAcs (7 sugars now)
  3. reorientation of the oligosaccaride into the lumen
  4. more mannoses from dolicholphosphomannose; glucose from dolicophosphoglucose
  5. we now have the core structure: 2 GlnNAcs linked to mannoses which are linked to 3 glucoses
  6. ribosome attaches to translocon and peptide chain grows
  7. core is transferred to an aspargine residue in the nascent polypetide chain
24
Q

What is the core structure considered to be in N-linked glycosylation?

A

dol phos + 2 GlcNacs linked to mannoses which are linked to 3 glucoses

25
Q

What AA does the core structure of N-linked glycosylation get transferred to?

A

asparagine

26
Q

Explain modification of N-linked glycosylated proteins?

A

enter the golgi and get re-glycosylated in two different ways:
high mannose
complex type

27
Q

Explain the 4 things made from o-linked glycosylation? (You might have to draw this out, Leslie.

A

in the golgi, glycosyltransferrases transger sugars to serine or threnoine

O antigen: Serine-Gal-GlcNAc-Gal-Fucose
A antigen: SErine-al-GlcNAc-Gal (2: Fucose and GalNac)
B antigen: serine-al-GlcNac-Gal (Fucose and Gal)
AB: BOTH A and B

28
Q

When does 0-linked glycosylation occur?

A

only when the fully folded protein reaches the Golgi

29
Q

What is this: serine-gal-GlcNac-Gal –> Fucose

A

O antigen

30
Q

What is the main part of an antigen?

A

serine-gal-GlcNac-Gal

31
Q

What antigen has Fucose and GalNac on it?

A

A antigen

32
Q

What antigen has fucose on it?

A

O antigen

33
Q

What antigen has fucose and gal on it?

A

B antigen

34
Q

There are 3 types of modifications that can occur at termini? What are they

A
  1. trimming at N terminus: not all proteins require a methionine; so this can get trimmed and changed
  2. addition of hydrophobic moeities: tethering
  3. at teh C-termnius: proteins are tethered to GPI anchor
35
Q

What is myristoylation?

A

myristic acid added to N-term glycine

36
Q

What is palmitoylation?

A

palmitic acid added to cysteinea

37
Q

What is prenylation?

A

isoprenoids added to cysteine at C term

38
Q

How does a cell know a protein needs to be brought to eh lysosome?

A

it has a man-6-P

39
Q

Where are mitochondrial proteins synthesized?

A

cytosol

40
Q

How do proteins get into the mitochondria from the cytosol?

A
  1. mit proteins synthesized as large preproteins with an N-term presequence
  2. chapersone stabilize unfolded form
  3. TOms and TIMS provide a channel though mit
  4. presequence cleaved
  5. go into inner or outer membranes
41
Q

2 organelles for degrading proteins?

A
  1. lysosome

2. proteasome

42
Q

If a protein is ubquitinized, where is it degraded?

A

proteasome

43
Q

What enzyme identifies proteins for ubiquitination?

A

E3

44
Q

What is the important fact about ubiquitination? what do you need?

A

POLY-ubiquinitination

Section 4 (7 decks)

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