Translation Flashcards
How many high energy bonds are used to create each peptide bond in translation?
Four. Two for attachment of an AA by the aminoacyl tRNA synthetases, and two for elongation.
What information does the mRNA hold in the translation process?
It is the code! Three letter codons of mRNA decided which AA goes where!
So if mRNA is the code, who reads it?
tRNA baby! They deliver the correct AA for each codon by base pairing with their anticodon region.
How can tRNAs often recognize multiple codons?
The wobble-pairing at the third location in the codon.
So how does tRNA get the right AA on its back?
Aminoacyl tRNA synthetases.
So what does that ribosome thing do?
This is the platform… Like platform 9 ¾ from HP.
What does the ribosome look like?
It has three tRNA binding sites, A, P, and E… so APE.
Which subunit of the ribosome has the catalytic center?
The large subunit… its a BIG catalytic center; the Peptidyl transferase center, PTC.
What are the two subunits of the ribosome in Eukaryotes?
40S and 60S subunits.
What are the two subunits of the ribosome in Prokaryotes?
30S and 50 S
What are the proteins called that help bring the ribosome to the message and assist in assembly of the machinery.
Initiation Factors
What proteins deliver tRNAs and move the ribosome down the message?
Elongation Factors (and their partners)
What proteins dissociate the subunits from the mRNA at the stop codon?
Termination/recycling factors
What site is the start codon (AUG) put in order to start Translation?
P-site
In bacteria, what sequence allows the ribosome to bind and where does binding occur?
Shine-Dalgarno sequence; right at the site of the start codon.
In Eukaryotes, where does binding of the ribosome occur, and what factor helps that occur?
EIF4E helps bind the ribosome to the 7-methyl guanosine cap of the 5’ end of the mRNA
What is the role of an IRES (Internal Ribosome Entry Site)?
IRESs are cap-independent processes to initiate translation.
Explain the A-P-E movement of tRNA in Translation.
The A site is the first site of binding, “reading” the message. The peptide bond is formed and the protein is moved from the P site to the A site. Translocation occurs moving the tRNA in the A site to the P site, it then translocates to the E site and eventually out of the ribosome.
A codon is changed to encode a different AA – what type of mutation am I?
Missense.
A codon is changed but the Same AA is encoded – what type of mutation am I?
Silent.
A codon is changed that shifts the reading frame (Addition/Deletion) – what type of mutation am I?
Frame-shift mutation.
A codon is changed making a premature stop codon – what type of mutation am I?
Nonsense mutation.
A codon is changed removing a stop codon – what type of mutation am I?
Sense Mutation.
How could a change in codon change the speed of production?
With varying levels of tRNA with varying binding affinities, it may be hard to find a tRNA with a specific codon, and could slow the speed of production.
How could the speed of initiation be regulated?
There could be occlusion of shine-delgarno (bacteria) or factors that inhibit scanning (eukaryotes).
How can different AUGs have different “strengths?”
Kozac Context;
How can translation be affected at the 5’ cap?
eIF4E can be bound by 4E Binding Proteins that block its function. Phosphorylation blocks their binding, allowing translation initiation.
What drug causes dephosphorylation of 4E-BPs and binding to eIF4E to stop translation?
Rapamycin
How is translation regulated by eIF2-Alpha?
When eIF2-alpha is phosphorylated, its activity is inhibited and it blocks initiation by blocking the initiator tRNA binding to the ribosome. This can be done by interferon in the cell (as a response to virus).
What types of regulation come from 3’ / 5’ UTRs?
All kinds? Binding interactions there do everything from mRNA stability to ribosome binding.
What two drugs target inhibiting the peptidyl transferase at the 60S subunit?
Cycloheximide, Anisomycin
What are the four drugs inhibiting peptidyl transferase at the 50S subunit?
Erythromycin, Linocomycin, Clindamycin, Chloramphenicol.
What drug inhibits tRNA binding at the A-site in prokaryotes?
Tetracycline aminoacyl
What drug inhibits initiation and elongation at the 30S subunit?
Streptomycin
What drug inhibits initiator tRNA binding at the 30S subunit?
Kasugamycin
What drug inhibits phosphorylation of the 4E-BP at MTOR?
Rapamycin
