Translation Flashcards
Ribosomes
not specific - can translate any mRNA
Prokaryotes (e.g. Bacteria)
3 rRNA + 56 proteins
30S + 50S subunits = 70S ribosome
Eukaryotes
4 rRNA + 82 proteins
40S + 60S subunits = 80S ribosome
The difference in ribosomal size is important when designing drugs
RNA types
rRNA - RNA polymerase I ~ 80% only a few types, many copies of each mRNA - RNA polymerase II ~ 2% 100,000s of types, a few copies of each tRNA - RNA polymerase III ~ 15% 100s of types, many copies of each
The Genetic Code
Is non-overlapping and comma less.
Triplet - 3 bases code for 1 amino acid.
Template is read 5’to3’ –> produces a N to C polypeptide chain extension.
Start and Stop Codons
Initiation - AUG (recognised by Methionyl tRNA)
Termination - UAA, UAG, UGA
tRNA
On the 3’OH an amino acid can be added - changes the tRNA to amino acyl tRNA
The anticodon = the tRNA sequence that is complimentary to the found on the mRNA
Wobble position on the tRNA
Base I is aspecific - e.g. I can match with U, C and A
a single tRNA species can recognise more than one codon
Translation Initiation
5’cap is being recognised
Requires energy
Starts coding at AUG
Translation elongation
Met is added at AUG codon at the P site
The A site is the acceptor site for the next amino acyl tRNA
Peptide bond formation - elongation of polypeptide chain at the A site
Ribosome moves along the RNA leaving the A site empty and ready for the next amino acyl tRNA
Translation termination
At a stop codon water is used to hydrolyse the peptide bond and free the ribosome
Bacteria
Simple promoters
Single RNA polymerase (humans have three)
No post transcriptional processing (no introns)
Shorter lived mRNA
Different translation factors
Differences allow drugs to target bacterial protein synthesis without damaging human protein synthesis
