Translation Flashcards
tRNA structure
~ simple cloverleaf structure
~ D-loop, T-loop and anti-codon loop
~ acceptor stem with a 3’ CCA tail
~ contains modified bases (T + D)
3’ CCA tail
added post transcriptionally
site of amino acid attachment
Aminoacylation/Charging
tRNA-amino acid attachment
~ uses ATP as a cofactor
~ a.a. attached to 3/2’ OH of terminal A of CCA tail
~ produces an aminoacyl-tRNA
~ each a.a./tRNA combo has its own enzyme
Wobble pairing
when the 3rd base in the codon/anti-codon shows flexibility in its base pairing
Method of specificity of aminoacyltransferases
- size exclusion of a.a from aminoacylation site
- editing pre-transfer in editing site (amino acid rejected)
- editing post-transfer editing site breaks bonds
IF1 and IF3
help guide the initiator tRNA to the right place on the small subunit
prevent binding of the large subunit
EF-Ts
exchanges GDP for GTP, regenerating EF-Tu
EF-Tu
elongation factor
~ forms a complex with GTP and aminoacyl-tRNA and helps it to bind tot he exposed codon in the A site
~ leaves after undergoing GTP hydrolysis
EF-G
helps the ribosome move along one codon in the 3’ direction
~ released after GTP hydrolysis
The peptide transferase reaction is catalysed by a …
ribozyme
Ribozyme
RNA section of the 50S subunit of the ribosome
~ involved with rRNA splicing and the removal of introns
Initiation
~ IF3 and IF1 are bound to the small ribosomal unit in the E and A sites
~ IF2 joins the mRNA and the small subunit together by hydrolysing GTP
~ a.a-tRNA binds to the P-site, releasing IF1-3 and causing the large ribosomal subunit to bind
Elongation
~ repeated steps of tRNA binding
~ insertion of a.a-tRNA at A site dislodges the uncharged tRNA at E site
~ peptide chain gets longer
Termination
~ when a stop codon is reached, a release factor (RF1 or RF2) binds to the stop codon in the A site
Recycling
~ ribosome recycling factor and EFG-GTP promote complex disassembly
~ IF3 binds to small subunit to stabilise it
