Lecture 18 Biochemistry
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What is the name for the sequence 6-10 bases upstream from the site where translation starts in prokaryotes? What binds to this location? What is the start codon sequence?
- 16S ribosomal RNA subunit (part of the 30S ribosomal subunit)
Is a kozak box found in prokaryotic or eukaryotic cells?
Where does the 40S ribosomal subunit first bind? What does it do?
It binds to the 5’ cap at the end of mRNA, it then moves down the mRNA until it reaches a section known as the kozak box. It then begins translation at AUG
What is the sequence for the kozak box?
What mutation causes cystic fibrosis?
3 base pair deletion that deletes F at position 508
What is the shine-dalgarno sequence on mRNA?
How does an amino acid become attached to tRNA?
It is charged by aminoacyl-tRNA synthetases, requiring 2 ATP
What is the total energy cost per peptide bond formed during translation?
2 ATP for the charging of amino acids and 2 GTP for the moving from site to site
How does streptomycin function?
It binds to the 30S subunit and distorts its structure, interfering with the initiation of protein synthesis
How does Puromycin function?
It bears a structural resemblance to aminoaacyl-tRNA and becomes incorportated into the growing peptide chain, halting elongation in both prokaryotes and eukaryotes
How do tetracyclines function?
They interact with the 30S ribosomal subunit, blocking access of the aminoacyl-tRNA to the A site of the mRNA ribosome
How does Chloramphenicol function?
- Inhibits prokaryotic peptidyltransferase
- High levels may also inhibit mitochondrial protein synthesis
How do clindamycin and erythromycin function?
Bind irreversibly to a site on the 50S ribosomal subunit on the bacterial ribosome, thus inhibiting translocation
How does diphtheria toxin function?
Inactivates the eukaryotic elongation factor, EF-2, thus preventing translocation
What is responsible for catalyzing the formation of peptide bonds the link amino acids in protein production?
The large ribosomal subunit
What is the small ribosomal subunit responsible for?
It binds mRNA and ensures proper pairing between codon and anti-codon
Which site of the small ribosomal subunit does the initiation codon bind? Which site do all other codons bind?
P site, after that they all bind to the A site
What does the initator tRNA carry in eukaryotes and in prokaryotes?
Met and fMet
Does the large subunit bind before or after the initiator tRNA binds the p site of the small ribosomal subunit?
Which reaction transfers the amino acid from the P site to the A site and allows for the peptide bond to form?
What moves the ribosome along mRNA and which direction does it move?
Translocase moves the ribosome in the 3’ direction
What are the termination codon sequences?
UGA, UAA, UAG
What binds in the A site when a termination codon is present, causing the peptidyl transferase to catalyze the transfer of H2O instead of an amino acid to the end of the polypeptide and thus releasing the protein?
What disrupts 28S rRNA by depurination?
What drug looks like aminoacyl-tRNA?
What drug disrupts translocation by inactivating eEF-2
What drug impairs initiation?
What drug impedes recruitment of aminoacyl-tRNA?
What drug inhibits peptidyl transferase?
What drug disrupts translocation by binding to the 50S unit?
Clindamycin and Erythromycin
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