Mechanistic features of translation

Question 1

Describe initiation in prokaryotes

Answer 1

Involves initiation factors IF-1,2,3.
IF-3 binds to 30S preventing 50S from attaching.
IF-1 binds in A site so fmet-tRNA goes to P site
Adding IF-2 and mRNA triggers GTP hydrolysis when 50S joins
Forms 70S, initiation factors released

Question 2

Describe elongation

Answer 2

There is codon directed binding of aminoacyl-tRNA

Causes peptide bond formation

Question 3

Describe peptide bond formation

Answer 3

Aminoacyl portion of fMet-tRNA transferred to AA group of aa residue in A site forming peptide bond
P site now has empty tRNA
A site now has extended polypeptide chain

Question 4

Describe termination

Answer 4

Bond between last aa and tRNA needs to be hydrolysed via release factors
Release factors bind to the vacant A site

Question 5

Describe initiation of protein synthesis in eukaryotes

Answer 5

Involves elF-4A,E,G
elF-4E binds to 5’ cap
elF-4A is a helicase that unravels the secondary structure so 40S can scan along mRNA
elF-4G links initiation complex

Question 6

Describe termination

Answer 6

If H20 binds to CCA arm which is a protein that mimics A site, then polypeptide released.

Question 7

Name translation control mechanisms

Answer 7

Regulation of initiation/elongation via phosphorylation

Protein product of gene binds to mRNA preventing initiation