Protein Synthesis, Modifications and Targeting Flashcards
Describe the function of rifamycin
Prevents RNA synthesis, binds to RNA polymerase to block initiation of RNA chains
A mutation in tumor suppressor mRNA would cause *****
a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis
b)
Describe the differences between prokaryotic and eukaryotic ribosomes
Prok - 70S, 50S and 30S subunits
Euk - 80S, 60S ad 40S subunits
Which of these acts on both prokaryotes and eukaryotes?
a) tetracycline
b) puromycin
c) streptomycin
d) actinomycin D
e) erythromycin
B and D
Polyubiquitinated chains target proteins to what two processes
proteasomal degradation
DNA repair
How do amyloid fibrils form?
Abnormal prion proteins (PRP) bump into normal prp proteins and cause conformational change –> PRP aggregate
Describe the function of actinomycin D
Binds DNA and blocks RNA polymerase movement
What are lysosomal proteins tagged wtih?
mannose 6 phosphate
During initiation of protein synthesis in eukaryotes, initiator tRNA binds to the small ribosomal subunit then moves along the RNA strand searching for what?
AUG (start codon)
What is the difference between multi and poly ubiquitylation?
Multi are ubiquitylated at different points, poly have multi ubiquitin chain
In mRNA that is incorrectly spliced to have premature stop codon, ____ proteins bind to each _____ and trigger nonsense mediated decay
upf, EJC (exon junction complex)
A loss of function mutation in oncogenic miRNAs would cause
a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis
b)
Name five ABX that act on prokaryotes solely
Tetracycline, streptomycin, chloramphenicol, erythromycin, rifamycin
Describe the function of tetracycline?
Blocks binding of tRNA to A site
Post-translational import occurs for cytosol proteins with what destiny?
- import into organelles: nucleus, mitochondria, chloroplasts or peroxisomes
Cotranslational import occurs when newly formed polypeptide is transferred across ___________
ER membrane
Phosphate on serine, threonine and tyrosine accomplishes what?
Drives assembly of a protein into larger complexes
How does proteasome degrade misfolded proteins
Ubiquitin is cleaved then the protein is moved into the core where ATPases unfold it and it is digested
Describe the function of cyclohexamine
Blocks translocation reaction on ribosomes (lrg ribosome does not move over)
Post-translational modifications are addition of __________________ to change chemical nature and/or make structural changes
biochemical function groups
A mutation on the target section of an oncogenic mRNA may cause ***
a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis
a) due to expression not being regulated
What is the function of tRNA?
interprets the mRNA code during translation
Describe the function of chloramphenicol and anisomycin. What is the difference between these two?
blocks peptidyltransferase rxn in ribosomes (no peptide bond formed)
Chloramphenicol only acts on bacteria, whereas anisomycin only acts on eukaryotes
In eukaryotes, what occurs to primary RNA transcript to allow translocation from nucleus to cytosol (3)
1) 5’ capping
2) RNA splicing of introns
3) 3’ polyadenylation
Acetyl on lysine
Helps activate genes in chromatin by modifying histones
Which of these acts on prokaryotes solely?
a) alpha-amantin
b) cylohexamine
c) anisomycin
d) tetracycline
Tetracycline
- all others act on eukaryotes only
If protein folding cannot be fixed by chaperone, what occurs?
Goes to protease pathway
What is added to mRNA after they have been completely spliced? (allows “test” round of translation to occur)
Exon junction complexes (EJC)
How is miravirsen used in treatement of infection with Hep C virus?
It is an anti-mir-122
Inhibits mir-122 as a complimentary RNA strand
Once the initiator tRNA finds the start codon, locks into P site of ribosome, _____ and other initiation factors dissociate, allowing large ribosomal subunit to bind. Aminoacyl tRNA bound to elongation factor _______ then enters free “A” site on ribosome
EIF2, EF-TU
Describe the function of streptomycin
blocks transition from translation initiation to chain elongation, causes miscoding
Describe the function of hsp70 as a chaperone
Hsp70 helps refold protein, utilizes ATP
Describe the function of hsp60 (chaperonin) in chaperoning protein folding
Chaperonin utilizes multiple ATP to bind and refold protein in an enclosed space
When the ribosome reaches the stop codon, what occurs?
- Release factor binds to the A site, releasing polypeptide
- large subunit and Initiator tRNA dissociate and are recycled
A loss of function mutation in tumor suppressing miRNAs would cause
a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis
a)
In proteasome degradation, how does proteasome recognize the proteins to be degraded?
Polyubiquitin chain
Describe the competing processes that monitor protein folding following synthesis
If protein is uncorrectly folded, two competing processes:
1) chaperone: hsp70 – if needed –> hsp60
2) digested by proteasome
Describe the function of alpha amantin
blocks mRNA synthesis by binding preferentially to RNA polymerase II
_________ simultaneously translate same mRNA molecule
Polyribosome
What occurs when tRNA anti codon matches the mRNA codon?
- GTU elongation factor dissociates
- Ribosome catalyzes formation of peptide bond
- Elongation factor binds to ribosome
- Hydrolysis of GTP switches ribosome back to accepting state
Why do some antibiotics have a deleterious effect on eukaryotic mitochondria and chloroplasts?
Because mitochondria and chloroplasts resemble prokaryotes in sensitivity to inhibitors
Co-translational import occurs for proteins with what destiny? (2)
- Polypeptides destined for endomembrane system
- Export from cell
Ubiquitin on lysine
Mono addn regulates transport of membrane proteins in vesicles
Poly chain targets a protein for degradation
miRNAs are powerful translational regulators. Describe the process by which they regulate translation (involves RISC)
- double stranded miRNA is cleaved by dicer enzyme in the cytosol then RISC attaches to both strands.
- RISC degrades one and the other guides RISC to specific mRNAs to match.
- Those that are extensive matches are degraded. those that aren’t have translation repression (eventually degraded)
Describe the function of erythromycin
Binds in exit channel or ribosome and prevents elongation of peptide chain
Describe the function of puromycin
Causes premature release of nascent polypeptide chains
Name three ABX that act on eukaryotes only
Alpha-aminitin, cyclohexamine, anisomycin
What occurs when tRNA anticodon does not match the mRNA codon?
It is rejected
What are resident ER proteins tagged with?
KDEL sequence
What is the order in the creation of a functional protein
- folding and cofactor binding
- covalent modification
- binding to other protein subunits
- mature functional protein
