17. Translation Flashcards
this RNA is used as a template
mRNA
this RNA is used as an adapter molecule that carries amino acid to the growing polypeptide chain
tRNA
codon consists of
3 bases
how many total codons
64
how many codons code for amino acids
61
stop codons
3
•UAG
•UAA
•UGA
Characteristics of the genetic code
- degenerate
- unambiguous
- nonoverlapping
- universal
multiple codons may code for the same aa
degenerate
a specific codon always code for the same amino acid
unambiguous
the codons are read in a continuing sequence of nucleotide triplets until translation stop codon is reached
nonoverlapping
it has been conserved from very early stages of evolution, with only slight diff in the manner the code translated
universal
assembly of components for translation
- 2 ribosomal subunits
- mRNA
- Aminoacyl tRNA containing first codon
- initiation factors (IF-1, IF-2, IF-3, elF)
- GTP (ATP for eukaryotes)
binding site for incoming aminoacyl tRNA
A site
this site is occupied by peptidyl tRNA
P site
occupied by the empty tRNA
E site
the first aminoacyl tRNA (exception) binds to
P site
peptide bond formation if catalyzed by
peptidyltransferase
termination of translation occurs when
one of the 3 termination codons move to the A ste
Pairing of the tRNA anticodon with the mRNA codon proceeds from the 5’ end of the codon. Once the first two positions are paired, exact base pairing of the third position is less critical.
tRNA wobble
addition of single amino acid to the polypeptide chain requires
cleavage of 4 high energy bonds from ATP and GTP
post translational modifications in translation
- removal of excess aa
- phosphorylation
- glycosylation
- hydroxylation
- ubiquitin marked- degraded by proteasomes
death cap
Amanita phalloides
toxin of amanita mushroom
peptide toxin
alpha-amanitin - inhibits RNA polymerase II
rmanifestations of amanita poisoning
gastrointestinal symptoms
acute liver failure
toxin of corynebacterium diptheriae , and MOA
diptheria toxin , exotoxin
• inactivates the eukaryotic elongation factor EF-2 , preventing translocation
–> local tissue destruction, pseudomembrane formation
