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QUIZ 4 > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

1
Q

start codon

A

AUG

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2
Q

stop codons

A

UGA, UAA, UAG

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3
Q

direction of protein synthesis

A

NH2 -> COOH; read 5’ to 3’

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4
Q

silent mutations

A

point mutation that does not alter amino acid

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5
Q

missense mutation

A

point mutation that results in amino acid substitution

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6
Q

nonsense mutation

A

point mutation that results in premature stop codon

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7
Q

frameshift mutation

A

insertion or deletion (1 or 2 bases) that alters the reading frame

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8
Q

tRNA

A

contains the anticodon to base pair with mRNA codon

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9
Q

DHU loop

A

site on tRNA that binds tRNA synthetase

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10
Q

tRNA synthetase

A

responsible for forming bond between codon and anticodon

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11
Q

anticodon loop

A

part of tRNA that pairs with mRNA codon

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12
Q

3’ acceptor site

A

region on tRNA that is where amino acid attaches

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13
Q

anticodon of tRNA base

A

will be the amino acid identity in translation, no matter what amino acid is attached to the tRNA

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14
Q

Wobble pairing

A

weak interaction between 3rd codon and first anticodon

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15
Q

two important consequences of aminoacylation

A

energetics and fidelity

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16
Q

energetics in aminoacylation

A

hydrolysis of the ester linkage between amino acid attachment site and tRNA to allow new amino acid attachment is energetically favorable (releases phosphates)

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17
Q

aminoacylation fidelity

A

affinity for specific amino acids and proofreading by use of acylation and hydrolytic sites (cleaves incorrect amino acids)

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18
Q

Valyl-tRNA synthetase

A

binding pocket that exclude isoleucine based on size and hydrolytic sites

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19
Q

each amino acid has _

A

one tRNA synthetase that couples to it

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20
Q

tRNA synthetase reaction

A

hydrolysis of two ATP phosphate bonds –> energy for protein synthesis stored in tRNA-amino acid bond

21
Q

bacteria ribosome

A

30S + 50S

22
Q

eukaryotic ribosome

A

40S + 60S

23
Q

small ribosome subunit

A

interacts with mRNA and translation factors

24
Q

large ribosome subunit

A

23S/28S is a ribozyme (peptidyl transferase)

25
Q

translation start site (bacteria)

A

determined by the Shine-Dalgarno sequence

26
Q

translation start site (eukaryotes)

A

eIF4F scans mRNA to find AUG, additional factors needed

27
Q

start site selection

A

mRNA, IF1, and IF3 and small ribosomal subunit associate

28
Q

IF2/eIF2

A

in the GTP-bound form, bind to charged initiator tRNA and to pre-initiation complex

29
Q

GTP hydrolysis by IF2/eIF2

A

stimulated by conformation of pre-initiation complex when codon:anticodon interaction is correct –> one GTP phosphate bond is cleaved for initiation

30
Q

completion of initiation

A

large ribosomal unit binds

31
Q

Shine-Dalgarno sequence

A

purine-rich region about 10 basepairs ahead of AUG

32
Q

steps in initiation of translation (prokaryotes)

A

IF1 binds to 30S and blocks A site –> IF3 binds prevents 50S from binding –> Shine-Dalgarno binds and positions AUG at P site –> IF2-GTP brings fMet-tRNA to P site to pair with AUG codon –> IF2 hydrolyzes GTP to GDP releasing IFs and promoting 50S binding

33
Q

GEFs

A

exchange GTP for GDP on GTPases

34
Q

IF2 will ONLY bind_

A

fMet-tRNA

35
Q

eIF2 (eukaryotes)

A

facilitates binding of initiating tRNA to 40S

36
Q

eIF4A

A

RNA helicase to unwind

37
Q

eIF4B

A

scans unwound mRNA to locate first AUG

38
Q

eIF4E

A

binds to 5’ cap of mRNA

39
Q

eIF2B

A

guanine exchange factor for eIF2

40
Q

protein kinase R (PKR)

A

activated by dsRNA or interferons; can phosphorylate eIF2, causing it to bind GEF more tightly –> results in less active eIF2, slowing protein synthesis to decrease replication of virus

41
Q

translation elongation (bacteria)

A

EF-Tu GTPase brings in aminoacyl-tRNA to A site –> GTP hydrolysis –> EF-Tu-GDP will now release tRNA –> peptidyl transferase binds fMet in P site with new amino acid in A site –> EF-G causes translocation

42
Q

EF-G

A

translocase

43
Q

EF-Ts

A

GEF for EF-Tu

44
Q

eukaryote elongation factors

A

eEF1-alpha is EF-Tu and eEF1-beta is EF-Ts; eEF2 is EF-G

45
Q

diphtheria toxin

A

targets eEF2 –> catalyzes ADP-ribosylation of eEF2 that blocks protein synthesis

46
Q

translation termination (bacteria)

A

RF1 and RF2 recognize the stop codons –> RF3 mediates release of ribosomal subunits

47
Q

eukaryote release factors

A

eRF1 binds termination codons and eRF3 promotes release

48
Q

puromycin

A

QUIZ 4 (5 decks)

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