lecture 9 recap Flashcards
prokaryotic ribosome is
70S (large subunit is 50S and small subunit is 30S)
eukaryotic ribosome is
80S (large subunit is 60S and small subunit is 40S)
tRNA first binds to the A site which is the
aminoacylated tRNA binding site
every thing shifts due to the
elongation factor
the peptide chain is passed to the new tRNA with the new amino acid on to which site
P site (polypeptide chain site)
the old tRNA move to which site
E site (exit site)
where does the small subunit of the ribosome bind
to the cap
the small subunit then scans the mRNA till it finds the
AUG then translation starts
sequence in front of the AUG is the
kozak consensus - CC(A/G)CC
it improves translation initiation
when does the large subunit join
when the small subunit has found the start codon
eIF4F complex comes in which contains
eIF4E, G and A
eIF4F complex comes in and binds to what
the cap
the poly A tail is bound by what
PABP (poly A binding protein)
the PABP comes round and binds to the
eIF4F
this makes the mRNA
circularised - helps the ribosome come back to the cap
which part of eIF4F links to the PABP
eIF4G
what does eIF4A do
its an ATPase and RNA helicase which opens up the structure before the AUG to allow the small subunit to scan along without blockage
small subunit is bound to what
eIF2
eIF2 is a
GTPase which forms the PIC with tRNA
when the AUG is recognised the GTP of eIF2 is
hydrolysed released phosphate
eIF2 then leaves and the 60S subunit comes in with
eIF5B (also a GTPase)
eIF5B GTP is hydrolysed and eI5FB is
released
next tRNA comes in with what
eEF1A which is coupled with GTP and tRNA docks in the A site
then there is peptide bond formation between the
2 amino acids
eEF2 comes along and helps what
translocation of the mRNA allowing the next tRNA to come in
termination:
when ribosome gets to stop codon what comes in and sits in the A sit
eRF1
the peptide is released from the tRNA and the 2 ribosome subunits are
pulled apart
low iron:
dont need storage proteins so theyre repressed
what binds to the region in 5 UTR leading to translational repression
IRP 1/2
transport proteins are upregulated IRP 1/2 binds to 3’ UTR causing what
mRNA stabilisation
irp =
iron responsive proteins
high iron:
iron binds to the IPR1 and IPR2 is
degraded
no binding to 5 or 3 UTR
