Translation - lecture 4 Flashcards Preview

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1

What does aatRNA stand for?

Aminoacyl - transfer RNA (basically tRNA)

2

What does it mean when tRNA is 'charged'?

Coupled with the correct amino acid

3

What is aminoacylation?

Covalently attach the correct amino acid to the tRNA ( as specified by the anticodon)

4

What does aaRSs stand for?

Aminoacyl-tRNA synthetases

5

How do aaRSs select the right tRNA to be acylated?

Recognisng specific rTNA identifiers present on the acceptor step and anticodon loop. Highly conserved sequences i.e, G1,G2,G3.

6

How does the tRNA attach to the ribosome?

Ribosomes select aa-tRNA based only on there codon - anticodon interactions

7

What ribosomes are made of?

Made of rRNA and ribosomal proteins. have 2 subunits ; large and small. Subunits are not self assembling. combine only in presence of mRNA and aatRNA

8

What are the 4 steps involved in chain initiation?

- Formation of 43S pre- initiation complex
- formation of the initiation complex
- positioning at the start codon
- association of large subunit

9

What are the 3 steps of polypeptide synthesis?

1 - chain initiation
2 - chain elongation
3 - chain termination

10

What does elF stand for?

Elongation factor

11

Mechanism of forming the 43S pre - ignition complex

40S - elF3 already bound with elF1A . Then elF2 binds coupled with tRNA via GTP. elf5 also binds

12

Binding the 43S complex to the mRNA

elF4 complex binds to the mRNA which causes the poly A tail to bind to this too.
pre- initiation complex binds to the elF4 complex

4E,4G and 4A bind first then 4B binds

13

Positioning the initiation complex at the start codon

- initiation complex unwinds mRNA using elF4 helicase
-initiation complex stops at the AUG start site

14

Association of the large subunit (60S)

irreversible GTP hydrolysis mediates the association of the 60S - elF6 to the small subunit by the action of elF5.
factor displacement

15

Whats happened after setting up the initiation complex?

ribosome formed with a methionine at the P position

16

First step of chain elongation

aatRNA binding. Binds to the A site on the ribosomes . This is mediated by ef1

17

Second step of chain elongation

GTP hydrolysis induces conformational change in the ribosome . EF1 dissociates.

18

Third step of chain elongation

Peptide bond formation. amino acid from P transferred to form peptide bond on the A site

19

fourth step of chain elongation

GTP hydrolysis moves the tRNAs left , positioning in the E and P sites instead

20

Termination of the chain

Release factors bind to stop condons.
This induces peptidyl transferase to transfer water instead of aatRNA. Release

21

What antibiotics inhibit translation in prokaryotes?

streptomycin and chloramphenicol

22

What antibiotics inhibit translation in eukaryotes

cycloheximide

23

What antibiotics inhibit translation in both prokaryotes and eukaryotes?

puromycin

24

what enzyme catalyses the formation of a peptide bond?

peptidyl transferase