Protein Synthesis Flashcards
Name the three stop codons
UAA, UAG, UGA
Mutation which changes sequence to a stop codon
nonsense mutation
Mutation which changes sequence but does not result in an amino acid change
silent mutation
Mutation which changes sequence and results in a different amino acid
missense mutation
Which arm of tRNA recognizes and binds to mRNA
Anticodon Arm
Which arm of tRNA is important for recognizing amino acids?
D Arm
Which terminus is the amino acid attachment site on tRNA?
3’
Which enzyme “charges” tRNA with their appropriate amino acid?
aminoacyl tRNA synthases
Most common “Watson Wobble” binding pair between codon and anti-codon?
G-U
What nucleotide in the third position of the tRNA anticodon contributes to the presence of a watson wobble effect?
Inosine
What precedes the initiation codon in bacterial mRNA?
Shine Dalgarno sequence
mRNA with more than one ribosome translating
Polysome
Major checkpoint in protein translation?
IF2 / eIF2
What is IF2’s importance?
IF2 is necessary for bringing together the large and small subunit. Needs the GTP to GDP cleavage for energy.
How is eIF-2 regulated?
Phosphorylation/dephosphorylation
What in eukaryotic translation initiation binds the poly-A tail and brings everything together for efficient translation?
PABP
Scanning for the start codon is dependent on…
ATP
tRNA binding site - A
Holds incoming tRNA
tRNA binding site - P
carries growing peptide chain
tRNA binding site - E
empty tRNA exists
Brings charged tRNA to the ribosome. Bound to GTP
eEF-1α
What happens when eEF-1α/GDP is released?
tRNA inserted into the A site (irreversible)
Which enzyme catalyzes the formation of peptide bonds in elongation?
peptidyltransferase
Which elongation factor promotes exchange of bound GDP on eEF-1α for GTP?
eEF-1βγ
What role do the 5’ and 3’ untranslated regions (UTR) play in translation?
They can bind regulatory proteins to modulate translation.
How is ferritin mRNA translationally regulated?
Iron regulatory protein (IRP) binds to the iron response element in 5’ UTR, blocking translation
Translation of ferritin mRNA is blocked under what condition?
iron is absent
What binds to the 3’ UTR of ceruloplasmin (copper-carrying protein) mRNA during inflammation, inhibiting ribosome recruitment.
GAIT
Proteins can bind to the _____ in order to direct mRNAs to particular cellular locations?
3’ UTR
Phosphorylation of eIF-2 and e-IF2B does what?
Blocks exchange of GDP for GTP. (Inhibits)
Antibiotic used to inhibit initiation by binding to and distorting the structure of the 30S ribosomal subunit (prokaryotic)
Streptomycin
Inhibits elongation by blocking access of the A site through interaction with the 30S ribosome subunit
Tetracyclines
Binds and inhibits the peptidyltransferase activity of the 50S ribosome, preventing the formation of peptide bonds and blocking elongation
Chloramphenicol
Inhibit translocation of the ribosome by binding to the 50S subunit, blocking elongation
Erythromcin and clindamycin
Structural analog of tyrosyl-tRNA. Enters the A site of the ribosome and is incorporated into the peptide causing premature release of the polypeptide (both prokaryotic and eukaryotic)
Puromycin
Binds and inhibits the peptidyltransferase activity of the 50S ribosome, preventing the formation of peptide bonds and blocking elongation (prokaryotic)
Chloramphenicol
Cleaves the adenine residue from the 60S subunit (eukaryotic), making it so that eEF-2 can’t bind
Ricin
Structural analog of tyrosyl-tRNA. Enters the A site of the ribosome and is incorporated into the peptide causing premature release of the polypeptide (both prokaryotic and eukaryotic)
Puromycin
Naturally occurring fungicide, interfering with the translocation step in protein synthesis, blocking eukaryotic translational elongation
Cyclohexamide
Cleaves the adenine residue from the 60S subunit (eukaryotic), making it so that eEF-2 can’t bind
Ricin
Provides favorable conditions for correct folding, prevents aggregation, and prevents misfolding of proteins. Proteins which remain improperly folded after translation are brought here.
Chaperonin
Three roles for protein cleavage in protein processing
1) removal of the initiator methionine at the N-terminus
2) N-terminal signal sequence targets proteins for transport. This can be cleaved
3) cleavage of large precursors forms active enzyme/hormone
Cataylzes interconversion between prolyl isomerases
Peptyidyl Prolyl Isomerase
Three types of lipid attachments during protein processing
1) N-myristoylation
2) prenylation
3) palmitoylation
Glycosylphosphatidylinositol (GPI) anchors attach proteins to which side of the ER membrane?
luminal
ER-associated degradation/quality control chaperones
Calnexin and calreticulin
Excess of unfolded proteins activates a signaling pathway. Leads to expansion of the ER, production of more chaperones, and apoptosis in extreme cases.
Unfolded protein response
What is the start codon’s amino acid in prokaryotes?
Formyl-methionine (methionine in eukaryotes)
eIF-2 binds to what subunit in the preinitiation complex?
43S preinitiation complex
What is the name of the kinase which can inhibit eIF-2
PKR
eEF-1alpha uses GTP to do what?
Bring the tRNA into the A site
What ubiquinates and targets shit for proteosome?
APC
Which side chain residue does ubiquitin add to?
Lysine
