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B1 > Protein Synthesis, Modifications and Targeting > Flashcards

Protein Synthesis, Modifications and Targeting Flashcards

1
Q

Describe the function of rifamycin

A

Prevents RNA synthesis, binds to RNA polymerase to block initiation of RNA chains

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2
Q

A mutation in tumor suppressor mRNA would cause *****

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

A

b)

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3
Q

Describe the differences between prokaryotic and eukaryotic ribosomes

A

Prok - 70S, 50S and 30S subunits

Euk - 80S, 60S ad 40S subunits

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4
Q

Which of these acts on both prokaryotes and eukaryotes?

a) tetracycline
b) puromycin
c) streptomycin
d) actinomycin D
e) erythromycin

A

B and D

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5
Q

Polyubiquitinated chains target proteins to what two processes

A

proteasomal degradation

DNA repair

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6
Q

How do amyloid fibrils form?

A

Abnormal prion proteins (PRP) bump into normal prp proteins and cause conformational change –> PRP aggregate

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7
Q

Describe the function of actinomycin D

A

Binds DNA and blocks RNA polymerase movement

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8
Q

What are lysosomal proteins tagged wtih?

A

mannose 6 phosphate

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9
Q

During initiation of protein synthesis in eukaryotes, initiator tRNA binds to the small ribosomal subunit then moves along the RNA strand searching for what?

A

AUG (start codon)

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10
Q

What is the difference between multi and poly ubiquitylation?

A

Multi are ubiquitylated at different points, poly have multi ubiquitin chain

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11
Q

In mRNA that is incorrectly spliced to have premature stop codon, ____ proteins bind to each _____ and trigger nonsense mediated decay

A

upf, EJC (exon junction complex)

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12
Q

A loss of function mutation in oncogenic miRNAs would cause

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

A

b)

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13
Q

Name five ABX that act on prokaryotes solely

A

Tetracycline, streptomycin, chloramphenicol, erythromycin, rifamycin

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14
Q

Describe the function of tetracycline?

A

Blocks binding of tRNA to A site

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15
Q

Post-translational import occurs for cytosol proteins with what destiny?

A
  • import into organelles: nucleus, mitochondria, chloroplasts or peroxisomes
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16
Q

Cotranslational import occurs when newly formed polypeptide is transferred across ___________

A

ER membrane

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17
Q

Phosphate on serine, threonine and tyrosine accomplishes what?

A

Drives assembly of a protein into larger complexes

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18
Q

How does proteasome degrade misfolded proteins

A

Ubiquitin is cleaved then the protein is moved into the core where ATPases unfold it and it is digested

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19
Q

Describe the function of cyclohexamine

A

Blocks translocation reaction on ribosomes (lrg ribosome does not move over)

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20
Q

Post-translational modifications are addition of __________________ to change chemical nature and/or make structural changes

A

biochemical function groups

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21
Q

A mutation on the target section of an oncogenic mRNA may cause ***

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

A

a) due to expression not being regulated

22
Q

What is the function of tRNA?

A

interprets the mRNA code during translation

23
Q

Describe the function of chloramphenicol and anisomycin. What is the difference between these two?

A

blocks peptidyltransferase rxn in ribosomes (no peptide bond formed)

Chloramphenicol only acts on bacteria, whereas anisomycin only acts on eukaryotes

24
Q

In eukaryotes, what occurs to primary RNA transcript to allow translocation from nucleus to cytosol (3)

A

1) 5’ capping
2) RNA splicing of introns
3) 3’ polyadenylation

25
Q

Acetyl on lysine

A

Helps activate genes in chromatin by modifying histones

26
Q

Which of these acts on prokaryotes solely?

a) alpha-amantin
b) cylohexamine
c) anisomycin
d) tetracycline

A

Tetracycline

- all others act on eukaryotes only

27
Q

If protein folding cannot be fixed by chaperone, what occurs?

A

Goes to protease pathway

28
Q

What is added to mRNA after they have been completely spliced? (allows “test” round of translation to occur)

A

Exon junction complexes (EJC)

29
Q

How is miravirsen used in treatement of infection with Hep C virus?

A

It is an anti-mir-122

Inhibits mir-122 as a complimentary RNA strand

30
Q

Once the initiator tRNA finds the start codon, locks into P site of ribosome, _____ and other initiation factors dissociate, allowing large ribosomal subunit to bind. Aminoacyl tRNA bound to elongation factor _______ then enters free “A” site on ribosome

A

EIF2, EF-TU

31
Q

Describe the function of streptomycin

A

blocks transition from translation initiation to chain elongation, causes miscoding

32
Q

Describe the function of hsp70 as a chaperone

A

Hsp70 helps refold protein, utilizes ATP

33
Q

Describe the function of hsp60 (chaperonin) in chaperoning protein folding

A

Chaperonin utilizes multiple ATP to bind and refold protein in an enclosed space

34
Q

When the ribosome reaches the stop codon, what occurs?

A
  • Release factor binds to the A site, releasing polypeptide

- large subunit and Initiator tRNA dissociate and are recycled

35
Q

A loss of function mutation in tumor suppressing miRNAs would cause

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

A

a)

36
Q

In proteasome degradation, how does proteasome recognize the proteins to be degraded?

A

Polyubiquitin chain

37
Q

Describe the competing processes that monitor protein folding following synthesis

A

If protein is uncorrectly folded, two competing processes:

1) chaperone: hsp70 – if needed –> hsp60
2) digested by proteasome

38
Q

Describe the function of alpha amantin

A

blocks mRNA synthesis by binding preferentially to RNA polymerase II

39
Q

_________ simultaneously translate same mRNA molecule

A

Polyribosome

40
Q

What occurs when tRNA anti codon matches the mRNA codon?

A
  • GTU elongation factor dissociates
  • Ribosome catalyzes formation of peptide bond
  • Elongation factor binds to ribosome
  • Hydrolysis of GTP switches ribosome back to accepting state
41
Q

Why do some antibiotics have a deleterious effect on eukaryotic mitochondria and chloroplasts?

A

Because mitochondria and chloroplasts resemble prokaryotes in sensitivity to inhibitors

42
Q

Co-translational import occurs for proteins with what destiny? (2)

A
  • Polypeptides destined for endomembrane system

- Export from cell

43
Q

Ubiquitin on lysine

A

Mono addn regulates transport of membrane proteins in vesicles
Poly chain targets a protein for degradation

44
Q

miRNAs are powerful translational regulators. Describe the process by which they regulate translation (involves RISC)

A
  • double stranded miRNA is cleaved by dicer enzyme in the cytosol then RISC attaches to both strands.
  • RISC degrades one and the other guides RISC to specific mRNAs to match.
  • Those that are extensive matches are degraded. those that aren’t have translation repression (eventually degraded)
45
Q

Describe the function of erythromycin

A

Binds in exit channel or ribosome and prevents elongation of peptide chain

46
Q

Describe the function of puromycin

A

Causes premature release of nascent polypeptide chains

47
Q

Name three ABX that act on eukaryotes only

A

Alpha-aminitin, cyclohexamine, anisomycin

48
Q

What occurs when tRNA anticodon does not match the mRNA codon?

A

It is rejected

49
Q

What are resident ER proteins tagged with?

A

KDEL sequence

50
Q

What is the order in the creation of a functional protein

A
  • folding and cofactor binding
  • covalent modification
  • binding to other protein subunits
  • mature functional protein

B1 (18 decks)

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