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SFM Exam 2 > 22: Protein Processing > Flashcards

22: Protein Processing Flashcards

1
Q

Cap and tail on mRNA

A

5’ cap: 7-methylguanosine

3’ Poly-A tail

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2
Q

Structure of tRNA

A

Cloverleaf with two regions of unpaired nts - the anticodon loop + 3’ CCA terminal region

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3
Q

Anticodon loop vs 3’ CCA terminal region

A

Anticodon loop: 3 nts that pair with a complementary codon in mRNA
3’ CCA terminal region: binds AA that matches the corresponding codonQ

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4
Q

Aminoacyl tRNA

A

TRNA + its respective AA

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5
Q

What enzyme activates AAs by adding them to tRNAs?

A

Aminoacyl tRNA synthetase

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6
Q

Two steps in AA activation

A
  1. Aminoacyl tRNA synthetase adds AMP to COOH end of AA

2. AA transferred to cognate tRNA

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7
Q

Eukaryotic vs prokaryotic ribosome subunits

A

Euk: 40S + 66S
Pro: 30S + 50S

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8
Q

Three sites on a ribosome

A

A: Acceptor: mRNA receives aminoacyl tRNA
P: Peptidyl: aminoacyl tRNA is attached
E: Exit: location occupied by empty tRNA before exiting ribosome

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9
Q

Polysomes

A

Clusters of ribosomes simultaneously translating a single mRNA molecule

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10
Q

In initiation, which part is assembled first?

A

Pre-initiation complex

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11
Q

Where does the initiator tRNA attach to?

A

P site of small subunit

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12
Q

What is bound to the initiator tRNA?

A

GTP

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13
Q

What is the initiator tRNA?

A

Met-tRNA

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14
Q

When does the large subunit add to the small one?

A

After tRNA-Met is already bound to P site

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15
Q

Initiation codon

A

AUG (Met)

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16
Q

Peptidyl transferase

A

Adds peptide bonds between AA in A and P sites

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17
Q

Three stop codons

A

UAA, UAG, UGA

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18
Q

RFs

A

Release factors; bind A site with stop codon and cleave ester bond stop the chain - forms COOH at the end of the polypeptide using water

19
Q

How does the ribosomal complex dissociate after use?

A

GTP hydrolysis

20
Q

Five prokaryotic translation inhibitors and what they bind to

A
  1. Streptomycin: 30S
  2. Clindamycin, erythromycin: 50S
  3. Tetracycline: 30S
  4. Chloramphenicol: peptidyl transferase
21
Q

Three functions of streptomycin

A
  1. Intereferes with fMet-tRNA binding
  2. Impairs initiation
  3. 30S + 50S cant bind
22
Q

Tetracycline function

A

Blocks entry of aminoacyl-tRNA into ribosomal complex

23
Q

Four eukaryotic translation inhibitors and what they bind

A
  1. Shiga toxin, Ricin: 60S
  2. Diphtheria toxin: GTP-bound EF-2
  3. Cyclohexamine: peptidyl transferase
24
Q

Shiga toxin and Ricin function

A

Block entry of aminoacyl-tRNA into ribosome

25
Q

One elongation inhibitor + function + eukaryotic or prokaryotic?

A

Puromycin: premature chain termination (in prokaryotes and eukaryotes)

26
Q

How does Puromycin work?

A

Resembles 3’ end of aminoacyl-tRNA -> enters A site and adds to growing chain, causing premature chain release

27
Q

What binds proteins on the way to mito to inhibit degradation?

A

HSP70

28
Q

Large vs small proteins going to the nucleus

A

Large need localization code, small ones can just pass through the nuclear envelope

29
Q

SRP

A

Signal recognition particle - wraps itself around ribosome/mRNA/peptide and connects it to ER - halts translation until part of peptide is inserted into the ER

30
Q

Only non-peptide protein localization code and for what location?

A

M6P for the lysosome

31
Q

Inclusion cell disease

A

Defective GlcNAc phosphotransferase -> no M6P added to proteins destined for the lysosomes

32
Q

Clinical symptoms of inclusion cell disease

A

Lysosomal enzymes secreted into blood -> failure to thrive and developmental delays by 6months, death usually by 7 years

33
Q

Chaperones vs chaperonins and examples of each

A

Chaperones: HSP70: help fold and protect proteins
Chaperonins: HSP60: barrel where proteins can fold in an ATP-dependent manner

34
Q

Proteolytic cleavage

A

Turning inactive or nascent proteins into their active or mature forms

35
Q

Four common post-translational modifications

A
  1. Phosphorylation
  2. Disulfide bonds
  3. Glycosylation
  4. Acetylation
36
Q

What proteins get glycosylated vs acetylate?

A

Glycosylation: extracellular proteins
Acetylation: histones

37
Q

Four residues affected by glycosylation

A

Ser, Thr, Asn, Gln

38
Q

Residue affected by acetylation

A

Lys

39
Q

Two mechanisms of glycosylation and on which residues they occur

A

O-linked: on hydroxyl groups of Ser or Thr

N-linked: on Asn or Gln

40
Q

Clinical issue with glycosylated proteins

A

Role in cataract formation

41
Q

How acetylation occurs

A

Uses acetyl coA as the acetyl donor group

42
Q

enzymes that add and remove acetyl groups

A

HAT: histone acetyltransferase: acetylate
HDAC: histone deacylase: deacytlate

43
Q

Are genes active or inactive when acetylate?

A

Active

SFM Exam 2 (19 decks)

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