Protein Synthesis, Modifications and Targeting Flashcards by Diana Padilla

Describe the function of rifamycin

Prevents RNA synthesis, binds to RNA polymerase to block initiation of RNA chains

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A mutation in tumor suppressor mRNA would cause *****

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

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Describe the differences between prokaryotic and eukaryotic ribosomes

Prok - 70S, 50S and 30S subunits

Euk - 80S, 60S ad 40S subunits

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Which of these acts on both prokaryotes and eukaryotes?

a) tetracycline
b) puromycin
c) streptomycin
d) actinomycin D
e) erythromycin

B and D

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Polyubiquitinated chains target proteins to what two processes

proteasomal degradation

DNA repair

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How do amyloid fibrils form?

Abnormal prion proteins (PRP) bump into normal prp proteins and cause conformational change –> PRP aggregate

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Describe the function of actinomycin D

Binds DNA and blocks RNA polymerase movement

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What are lysosomal proteins tagged wtih?

mannose 6 phosphate

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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)

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What is the difference between multi and poly ubiquitylation?

Multi are ubiquitylated at different points, poly have multi ubiquitin chain

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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)

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A loss of function mutation in oncogenic miRNAs would cause

a) tumorigenesis
b) increase in tumor supressor proteins and decreased tumorigensis

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Name five ABX that act on prokaryotes solely

Tetracycline, streptomycin, chloramphenicol, erythromycin, rifamycin

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Describe the function of tetracycline?

Blocks binding of tRNA to A site

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Post-translational import occurs for cytosol proteins with what destiny?

import into organelles: nucleus, mitochondria, chloroplasts or peroxisomes

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Cotranslational import occurs when newly formed polypeptide is transferred across ___________

ER membrane

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Phosphate on serine, threonine and tyrosine accomplishes what?

Drives assembly of a protein into larger complexes

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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

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Describe the function of cyclohexamine

Blocks translocation reaction on ribosomes (lrg ribosome does not move over)

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Post-translational modifications are addition of __________________ to change chemical nature and/or make structural changes

biochemical function groups

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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

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