Translation Flashcards
4 levels of protein organization
Primary
-sequence of amino acids
Secondary
-amino acid interactions cause primary structure to fold, ex: beta sheet or alpha helix
Tertiary
-folded further
Quaternary
2+ polypeptide chains to make functional protein
What is degeneracy in the genetic code?
-flexibility in binding at the 3rd codon position (1st anti-codon position), known as wobble position
-wobble allows tRNA anti-codon to bind to either codon which specify for same amino acid
How do amino acids join to tRNA?
Amino-acyl tRNA synthetase
- amino acid reacts with ATP, producing aminocyl-AMP
- amino acid transferred to tRNA, AMP is released
Initiation of Translation in Prokaryotes
16S rRNA (component of 30S) has complement to Shine-Delgarno sequence in the mRNA. This pairing positions ribosome near AUG
- IF-3 inhibits 50S from binding 30S
- IF-1 and IF-2 position (f)-met over start codon
- GTP hydrolized to GDP
- IF factors dissociate
- 70S complex now formed
Initiation of Translation in Eukaryotes
-initiator complex forms at 5’ of mRNA (7-MG cap)
-ribosome initiation complex scans inward for first AUG codon
-Kozak sequence influences the efficiency of which AUG to use
-poly(A) tail of mRNA interacts with mRNA 5’ 7-MG cap through cap-binding protein to promote translation initiation
Elongation in Translation
-charged tRNA enters A site of ribosome, this requires complex formation between aminoacyl tRNA, EF-Tu and GTP
-GTP to GDP and released with EF-Tu
-rRNA in large subunit catalyzes formation of peptide bond between amino acids
-EF-G and GTP required to move ribosome
-(F)-met now in E site, leaves to cytoplasm
-repeats
Termination in Translation
-occurs when stop codon enters A-site
-RF binds to A-site
-RF 1 and RF 2 recognize the stop codons, and promote cleavage of polypeptide chain from tRNA
-RF-3 and GTP bind to ribosome to assist in the dismantling
