Protein Synthesis

Question 1

start codon

Answer 1

AUG

Question 2

stop codons

Answer 2

UGA, UAA, UAG

Question 3

direction of protein synthesis

Answer 3

NH2 -> COOH; read 5’ to 3’

Question 4

silent mutations

Answer 4

point mutation that does not alter amino acid

Question 5

missense mutation

Answer 5

point mutation that results in amino acid substitution

Question 6

nonsense mutation

Answer 6

point mutation that results in premature stop codon

Question 7

frameshift mutation

Answer 7

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

Question 8

tRNA

Answer 8

contains the anticodon to base pair with mRNA codon

Question 9

DHU loop

Answer 9

site on tRNA that binds tRNA synthetase

Question 10

tRNA synthetase

Answer 10

responsible for forming bond between codon and anticodon

Question 11

anticodon loop

Answer 11

part of tRNA that pairs with mRNA codon

Question 12

3’ acceptor site

Answer 12

region on tRNA that is where amino acid attaches

Question 13

anticodon of tRNA base

Answer 13

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

Question 14

Wobble pairing

Answer 14

weak interaction between 3rd codon and first anticodon

Question 15

two important consequences of aminoacylation

Answer 15

energetics and fidelity

Question 16

energetics in aminoacylation

Answer 16

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

Question 17

aminoacylation fidelity

Answer 17

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

Question 18

Valyl-tRNA synthetase

Answer 18

binding pocket that exclude isoleucine based on size and hydrolytic sites

Question 19

each amino acid has _

Answer 19

one tRNA synthetase that couples to it

Question 20

tRNA synthetase reaction

Answer 20

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

Question 21

bacteria ribosome

Answer 21

30S + 50S

Question 22

eukaryotic ribosome

Answer 22

40S + 60S

Question 23

small ribosome subunit

Answer 23

interacts with mRNA and translation factors

Question 24

large ribosome subunit

Answer 24

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

Question 25

translation start site (bacteria)

Answer 25

determined by the Shine-Dalgarno sequence

Question 26

translation start site (eukaryotes)

Answer 26

eIF4F scans mRNA to find AUG, additional factors needed

Question 27

start site selection

Answer 27

mRNA, IF1, and IF3 and small ribosomal subunit associate

Question 28

IF2/eIF2

Answer 28

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

Question 29

GTP hydrolysis by IF2/eIF2

Answer 29

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

Question 30

completion of initiation

Answer 30

large ribosomal unit binds

Question 31

Shine-Dalgarno sequence

Answer 31

purine-rich region about 10 basepairs ahead of AUG

Question 32

steps in initiation of translation (prokaryotes)

Answer 32

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

Question 33

GEFs

Answer 33

exchange GTP for GDP on GTPases

Question 34

IF2 will ONLY bind_

Answer 34

fMet-tRNA

Question 35

eIF2 (eukaryotes)

Answer 35

facilitates binding of initiating tRNA to 40S

Question 36

eIF4A

Answer 36

RNA helicase to unwind

Question 37

eIF4B

Answer 37

scans unwound mRNA to locate first AUG

Question 38

eIF4E

Answer 38

binds to 5' cap of mRNA

Question 39

eIF2B

Answer 39

guanine exchange factor for eIF2

Question 40

protein kinase R (PKR)

Answer 40

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

Question 41

translation elongation (bacteria)

Answer 41

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

Question 42

EF-G

Answer 42

translocase

Question 43

EF-Ts

Answer 43

GEF for EF-Tu

Question 44

eukaryote elongation factors

Answer 44

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

Question 45

diphtheria toxin

Answer 45

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

Question 46

translation termination (bacteria)

Answer 46

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

Question 47

eukaryote release factors

Answer 47

eRF1 binds termination codons and eRF3 promotes release

Question 48

puromycin