Translation 2 Flashcards
What are the three sites for ribosome binding/holding/releasing tRNA?
A, P, and E. Indicates the order that the tRNA moves through the ribosome.
What is the Shine-Dalgarno Sequence?
GGAGG - located near the AUG start codon in prokaryotic sequences. Serves to align the ribosome w/ start site for translation
What is the first aa incorporated into a protein in prokaryotes?
fMet, which is a formylated form of methionine - formyl group put onto methionine after it is in the tRNA
How do peptides leave ribosomes?
As they are being synthesized via a tunnel in the structure
How does initiation of protein synthesis start?
With binding of initiation factor proteins (IFs - IF1 and IF3) to the 30S ribosomal unit.
What is the result of initiation?
16S rRNA is aligned w/ Shine-Dalgarno site of the mRNA
What are the factors in initiation and elongation?
G-Proteins.
What do G-Proteins do?
Bind to guanosine nucleotides and use GTP energy for their actions
IF2 (when bound to GTP) does what?
Carries the Met-tRNAf to the P site of the 30S subunit and pairs it with the AUG start codon
What happens with binding of 50S subunit to the 30S/mRNA?
Yields the 70S initiation complex w/ Met-tRNAf in the P site and the A and E sites will open
What is the start of elongation?
70S initiation complex. At this point, EF-Tu carries a charged tRNA to the A site of the complex. If the tRNA anticodon pairs properly, it stays matched w/ the codon and GTP is hydrolyzed, causing EF-TuGDP to release.
What happens if the tRNA anticodon does not form a stable base pair w/ the 70s initiation complex?
The entire charged tRNA-EF-Tu-GTP complex dissociates
What does the EF-Tu do to the amino acid and tRNA?
It protects the bond between them from being broken by water
Where does the peptide group go next?
It transfers from the P to become covalently linked via peptide bond to the amino acid on the tRNA in the A site.
What catalyzes this transfer from P to A?
The enzyme peptidyltransferase
