Biochemistry - Translation Flashcards
What is the mechanism of diptheria toxin and its relationship to protein translation?
Diptheria becomes infected by a bacterial virus.
ADP-ribose binds to the EF-2, which prevents elongation of the polypeptide chain.
Obviously, this is bad since we can’t synthesize proteins.
What is EF-2? What is EF-G
EF-2: Euks
EF-G: Proks
** EF is a GTPase protein. Hydrolysis of GTP is important for efficient translocation of the mRNA relative to the ribosome.
Why do we use less than 61 tRNA’s?
One tRNA can recognize multiple codons
What is the difference between 30/50/70s & 40/60/80s?
Prok vs. euk mRNA
Euk mRNA is more complex
What is the P site & A site in translation on a ribosome?
P site: has a free carboxyl end & holds the peptide [this is the charged site]
A: has the aminoacyl tRNA codon
What is ribozyme?
Peptide bond formation is catalyzed by the enzymatic activity of the RNA portion of the 50s ribosome
When does diptheria become toxic?
When it is infected with a lysogenic phage, aka a bacterial virus
What is the start codon(s)?
AUG
What is the stop codon(s)?
UGA, UAG, UAA
What is special about the “wobble position” on tRNA?
It can have an ionosine, which permits versatile base pairing, i.e. between two purines!
What do prokaryotes use as the first AA in a protein?
fMet
What diffuses into the A-site in order to terminate elongation?
RF, or release factor
Allows peptidyl transferase to cleave the ester bond between the RNA & the peptide
T/F Release factor (peptidyl transferase activity) is GTP dependent
True
What are the 4 major differences between prokaryotic and eukaryotic translation?
- Prok - polycistronic
- Prok - fMet
- Prok - multiple AUG start sites
- Prok - coupled transcription & translation
T/F Eukaryoties use a formylated-Methionine as its first codon in translation
False
What prevents abnormal protein folding during translation?
Chaperone proteins
T/F Modifications to an antibiotic may alter bacterial resistance to the drug or change absorption or clearance patterns
True
What is streptomycin?
Inhibitor of initiation
- Aminoglycoside structure
- Prevents assembly of ribosome (binds to 30s subunit)
What is tetracycline? State 3 examples
Inhibitor of elongation
* 4-ring structure
* Prevent aminoacyl-tRNA access to the A-site
Examples: minocycline, doxorubicin, doxycycline
What is erythromycin?
Inhibitor of elongation
- Macrolide structure
- Binds to 50s subunit of 70S ribosome
- Blocks elongation by preventing ribosome movement relative to the mRNA (translocation)
What is chloramphenicol?
Inhibitor of elongation
- Inhibits peptidyl transferase activity
- May inhibit mitochondrial activity [developing countries b/c it can damage the human – but it’s cheap!]
- Important for meningitis
What is cycloheximide?
Inhibitor of elongation
- Same action as chloramphenicol, but is extremely toxic to eukaryotes
- Prokaryotes and mitochondria not affected
- Used widely in labs
What is puromycin?
Inhibitor of elongation
- Structural analogue to a portion of amino-acyl tRNA
- Peptide can form -NH3 group, but gets stuck
- Causes peptide to fall out of the ribosome P-site
- Toxic to prokaryotes & eukaryotes
Which 2 elongation drugs are similar (one toxic to proks & one toxic to euks)
Proks- Choramphenicol
Euks- Cycloheximide
What is the difference between amino-acyl tRNA, ribozyme & peptidyl transferase?
Amino-acyl tRNA is bound to the A site with a free carboxyl end
Peptidyl transferase - forms peptide bonds (regulated by ribozyme)
The insulin receptor has this type of modification
Protein phosphorylation by a tyrosine kinase
What is O-linked glycosylation?
Adding a phosphate to an -OH group of Ser/Thr
What is N-linked glycosylation? What are the 2 types?
Adding a phosphate to an asparagine residue (2 types: mannose or complex)
The insulin receptor is this type of kinase
Tyrosine
In lipid anchoring, the cell targets what in order to anchor it to the plasma membrane?
Ras
When blood glucose is high, insulin will bind to this receptor.
Tyrosine kinase
