B2.053 Prework 1 Protein Translation Flashcards Preview

MCM Test 3 > B2.053 Prework 1 Protein Translation > Flashcards

Flashcards in B2.053 Prework 1 Protein Translation Deck (30)
Loading flashcards...
1

where do translation initiating complexes assemble?

7-methyl guanosine cap of mRNA

2

what is the function of the cap binding complex?

recruits small subunit of ribosome to mRNA
adaptor between the cap and ribosome

3

what is the name of the cap binding complex?

eIF4F

4

what 3 subunits make up eIF4F?

eIF4A eIF4G eIF4E

5

which subunit of the cap binding complex is limiting?

eIF4E

6

discuss the function of each subunit of eIF4F complex

eIF4E = binds to m7G-CAP, limiting subunit
eIF4G = scaffold
eIF4A = helicase

7

what is the initial recognition event that sets translation into motion?

cap complex eIF4F binds to mRNA cap

8

what is the second initiation event?

eIF2 loads methionyl-tRNA onto small ribosomal subunit

9

what % of translation starts w methionine?

95%

10

which factors mediate the interaction between eIF4F and the small ribosomal subunit?

eIF1
eIF3

11

what does the small ribosomal subunit do after binding to eIF4F?

scans along mRNA until the recognition of the start codon AUG

12

what happens once the start codon is encountered by the small ribosomal subunit?

the initiation factors are release and the large ribosomal subunit binds (elongation commences)

13

what is PABP?

poly A binding protein
interacts with polyA tail and cap binding complex

14

why is PABP useful?

drastically improves translation of mRNA
keeps ribosomes/eIFs near?
circularization of ribosome bound mRNA

15

how long is the polyA tail?

150-200 As

16

what makes up the 60S subunit?

28S rRNA
5S rRNA
5.8S rRNA
49 proteins

17

what makes up the 40S subunit?

18S rRNA
33 proteins

18

what are the 3 sites on the ribosome?

A site: aminoacyl
P site: peptidyl
E site: empty

19

what happens in the A site?

tRNA for the next codon enters

20

what happens in the P site?

site of the growing peptide chain attached to tRNA

21

how do toxins inhibit ribosome function?

rRNA N-glycosylase, cleaves N-glycosidic bond of adenine at position 432 in 28S rRNA
loss of protein synthesis results

22

which toxins inhibit rRNA function?

shiga toxin (bacteria)
ricin toxin (castor bean)

23

what factor is required for translocation/elongation?

EF2

24

how does EF2 work?

hydrolyzes 1 GTP per translocation to move the ribosome

25

what are diphtheria toxin and exotoxin A?

catalyze ADP ribosylation of EF2, blocking GTP hydrolysis
shuts down ALL translation
among the most toxic proteins that exist

26

what is EF1?

elongation factor 1
escorts next tRNA to the vacant A site
hydrolyzes one GTP per amino acid

27

what is important about the ester bond on the acceptor stem of a tRNA?

it is a high energy bond which is utilized in the formation of the peptide bond in protein synthesis

28

what catalyzes the peptide bond formation?

peptidyl transferase
23S rRNA of the large ribosomal subunit is catalytic molecule

29

what happens following peptide bond formation?

the nascent peptide shifts from P to A site
ribosome translocates to the next codon, moving the nascent peptide back to the P site

30

what happens when the ribosome reaches the stop codon?

RF binds A site
catalyzes release of protein from tRNA
disassembly of ribosome with subunit recycling