BGM1002/L19 Translation II Flashcards
What are ribosomes made of?
Ribonucleoprotein (RNA-protein)
How abundant are ribosomes?
10% of total protein
80% RNA
Describe the composition of 70S ribosomes.
50S + 30S subunits
What does the āSā in 70S stand for?
Svedberg unit
Measure sedimentation rate in a centrifuge thus size and shape
Describe the structure of the 50S ribosomal subunit.
31 different L proteins
23S rRNA
5S rRNA
Describe the structure of the 30S ribosomal subunit.
21 S proteins
16S rRNA
What is required for translation initiation?
Initiation factors IF1, IF2, IF3 and GTP
Initiator tRNA: fMet-tRNA^fMet
What is required for translation elongation?
Elongation factors EF-Tu, EF-Ts, EF-G and GTP
What is required for translation termination? (2)
Stop codon
Release factors RF1 and RF2
What is the name of initiator tRNA in bacteria?
N-formylmethionine (fMet)
What happens to methionine once it is removed from the initiator tRNA?
Formyl group transferred to methionine by formyltransferase
Which part of the ribosome binds to Shine Dalgarno sequence/ribosome binding site to initiate translation?
30S subunit
Where does initiator tRNA bind to initiate transcription?
Start codon AUG
Name the 3 sites of the ribosome involved in initiation of translation.
A site: amino acyl site
P site: peptidyl site
E site: exit site
What binds to form the 70S ribosomal complex?
50S and 30S ribosomal subunits
How is the 30S ribosomal subunit positioned on the 16S rRNA?
Base pairing between Shine Dalgarno sequence and 16S rRNA
Where do IF1 and IF3 bind?
30S subunit
Where does IF2 bind?
Complex with GTP
How is IF3 released from 30S ribosomal subunit?
Charged initiator tRNA binds to mRNA
What displaces IF1 and IF2 during initiation? What is produced?
50S ribosomal subunit
GDP + Pi
Describe the process of translation elongation. (3)
Aminoacyl tRNA binds to A site
Peptide bond formation
Translocation
What is required for delivery of charged tRNA to the A site?
EF-Tu, EF-Ts + GTP
What is required for translocation of RNA through ribosomes?
EF-G + GTP
What occurs when GTP is hydrolysed in the presence of EF-Tu?
EF-Tu-GDP complex forms
How is the EF-Tu-GDP complex broken down?
EF-Ts exchanges GDP for GTP
Describe peptide bond formation in translation. (2)
Amino group of aminoacyl-tRNA attacks carbonyl group of ester linkage of peptidyl-tRNA
Deacylated tRNA released
What sequences does RF1 recognise?
UAA and UAG
What sequences does RF2 recognise?
UAA and UGA
What does RF3.GTP do?
Helps RF1 and RF2 conduct termination
What is the role of RRF and EF-G?
Promote dissociation of ribosome
How is the energy for termination provided?
GTP hydrolysis
