L17 translation 2

What does polycistronic mRNA mean

One mRNA encodes multiple proteins

What can multiple ribosomes do on one mRNA

Translate it simultaneously

What is coupling of transcription and translation

Occur at the same time in prokaryotes

What is the first amino acid in eukaryotic translation

Methionine

Is methionine formylated in eukaryotes

No

What helps ribosome bind mRNA in eukaryotes

Seven methyl guanosine cap

What sequence helps identify start codon in eukaryotes

Kozak sequence

What is the Kozak consensus sequence

RXXAUGG

What is the function of the five prime cap

Stabilises mRNA and aids translation

What is the function of the polyA tail

Stabilises mRNA and prevents degradation

What are UTRs

Untranslated regions of mRNA

What are eIFs

Eukaryotic initiation factors

How many eIFs are identified

Twelve

What does eIF4E do

Binds the mRNA cap

What does eIF4G do

Acts as scaffold linking cap and polyA tail

What structure is formed by eIF4G interactions

Closed loop mRNA

What recruits the small ribosomal subunit in eukaryotes

eIF4G and eIF3 interaction

What does the pre initiation complex do

Scans for start codon

What is the role of eIF4A and eIF4B

Helicase activity to unwind mRNA

What energy source is used during scanning

ATP

What happens when start codon is found

eIF2 hydrolyses GTP

What does eIF2 GTP hydrolysis cause

Conformational change

What happens after conformational change

Large subunit binds

What happens to eIFs after initiation

Most are released

What is eEF1A equivalent to

EFTu

What is the function of eEF1A

Binds aminoacyl tRNA and GTP

What is eEF1B equivalent to

EFTs

What is the function of eEF1B

Exchanges GDP for GTP

What is eEF2 equivalent to

EFG

What is the role of eEF2

Ribosome translocation

What factor recognises stop codons in eukaryotes

eRF1

What does eRF1 mimic

tRNA

What happens after termination

Ribosome is recycled

Why do some antibiotics not affect human cells

They target seventy S ribosomes

Where else are seventy S ribosomes found in humans

Mitochondria

What does fusidic acid inhibit

Translocation step

What does fusidic acid bind

EFG GDP complex

What effect does fusidic acid have on ribosome

Blocks A site

What does puromycin mimic

Aminoacyl tRNA

What happens when puromycin enters ribosome

Premature chain termination

Why is puromycin released

It is not anchored in A site

What does diphtheria toxin target

eEF2

What reaction does diphtheria toxin catalyse

ADP ribosylation

What cofactor is used by diphtheria toxin

NAD plus

What is the effect of diphtheria toxin

Blocks protein synthesis

What is ricin

Ribosome inactivating protein

Where is ricin found

Castor bean seeds

How can ricin enter cells

Via lectin binding to galactose

What does ricin chain A do

Depurinates rRNA

What part of rRNA is targeted by ricin

Twenty eight S rRNA

What is the effect of ricin on ribosome

Inactivates it

What is common between prokaryotic and eukaryotic translation

Same genetic code

What molecules deliver amino acids in both systems

Aminoacyl tRNA

What is similar about ribosomes in both systems

Structure and function

What steps are similar in both systems

Elongation and termination

Why can transcription and translation not be coupled in eukaryotes

They occur in different compartments

What is different about initiation in eukaryotes

More complex mechanism

What modifications are important in eukaryotic mRNA

Five prime cap and polyA tail

What is the effect of protein synthesis inhibitors

Cause cell death