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MBG > Translation > Flashcards

Translation Flashcards

1
Q

start codon

A

AUG

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2
Q

stop codons

A

UAA, UAG, UGA

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3
Q

T/F. All codon triplets code for an amino acid

A

False, not stops

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4
Q

Why are translation errors more frequent than replication?

A

Not as big of a deal (heritability) and also not as robust proofreading mechanisms

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5
Q

how many tRNA synthetases?

A

20

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6
Q

what are three main chemical step of tRNA synthetase activity?

A
  1. Activation of AA with AMP
  2. Transfer of AA onto CCA end
  3. Exergonic pyrophosphate hydrolysis
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7
Q

How is unstable acyl bond of initiator tRNA resolved in eukaryotes?

A

binding by eIF2 loader stabilizes

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8
Q

how do synthetases recognize tRNAs? (3)

A
  1. Can look at anticodon
  2. Acceptor stem (serine)
  3. U-G wobble bp at position 3/7 (alanine)
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9
Q

how do synthetases do proofreading?

A

hydrolytic site on enzyme where inappropriately charged tRNAs are deacylated (because the pocket is not filled and external water can come in)

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10
Q

T/F. Ribosome catalytic core comprised of RNA and proteins

A

False, only RNA

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11
Q

characteristics of ribosomal proteins

A

Globular domain and long stringy domain, involved in structural stability

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12
Q

proteins involved in mRNA circularization in eukaryotes

A

eIF4E (cap binding), eIF4G (scaffold) and PABP (binds polyA)

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13
Q

scanning mechanism of 40S (euk)

A
  1. First AUG pretty much always read
  2. Initiator tRNA preloaded on 40S with other IFs - mainly eIF2, when AUG found, then GTP hydrolysis and large subunit joins
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14
Q

translation elongation (3 steps)

A
  1. A site loaded (eEF1)
  2. Rejection happens or not (two steps possible for pre and post GTP hydrolysis)
  3. eEF2 catalyzes ribosomal translocation
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15
Q

aminoglycoside mechanism of action

A

miscoding antibiotics, decreases sensitivity of codon:anticodon recognition

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16
Q

ways to get antibiotic resistance? (3)

A
  1. mutation of rRNA gene
  2. mutate rRNA proteins
  3. mutate enzymes that can degrade antibiotics
17
Q

translation inhibitors?

A

bind to active (A) site to inhibit - actinomycin D, puromycin, aminoglycosides, cyclohexamide

18
Q

what do termination factors bear a striking resemblance to?

A

tRNAs

19
Q

translocation

A

A site must be emptied, EF-G (eEF2) couples GTP hydrolysis and translocation

20
Q

regulation of initiation (bacteria)

A

stringent response - senses depletion of AA and responds with deacylated tRNA binding to A site of ribosome, recruiting RelA and making ppGpp, a global regulator

21
Q

eIF2

A

binds to initiator tRNA, alpha phosphorylation of it a common response to stress. Gets ribo to first AUG

MBG (13 decks)

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