Protein processing Flashcards
What is the RNA start codon for translation and what does it code for?
AUG- Methionine
What are the three RNA stop codons
UAA, UAG, UGA
What is a silent mutation?
A mutation that does not result in a change in the amino acid
What is a missense mutation?
A mutation that results in a change in the AA that can either have no effect or drastic change in protein folding
What is a nonsense mutation?
A mutation that changes the codon to a stop codon resulting in premature termination of protein synthesis
What is a frameshift mutation?
A mutation that causes multiple changes to the codon sequence
What is the mutation in sickle cell anemia and the physiological effect?
Glu (hydrophilic) to Val (hydrophobic) at the human beta globin gene. This results in deformed proteins that are rod-like and will aggregate. These cells have poor oxygenation and will clog arteries.
What kind of mutation results in sickle cell anemia?
a missense mutation- Glu for Val- results in misfolded protein
What is Duchenne Muscular Dystrophy?
Dystrophin gene is dysfunctional due to an out of frame mutation- Leads to muscle wasting and death
What kind of mutation results in Duchenne Muscular Dystrophy?
An out of frameshift mutation that leads to non functioning dystrophin gene
What kind of mutation results in Becker Muscular Dystrophy?
An in frame mutation of the dystrophin gene that results in a truncated dystrophin protein
What two things are added to mRNA to “protect” the sequence?
5’cap and poly A tail
What is the secondary structure and two crucial sites of the tRNA?
Shaped like a cloverleaf with an anticodon region to pair with complementary strand and 3’CCA terminal region that binds the AA for corresponding codon
How do tRNAs become activated?
Through aminoacyl synthetases- uses ATP to bond tRNA to the COOH end of the AA
What are the ribosomal subunits in prokaryotes?
50S large subunit and 30S small subunit- 70s when combined
What are the ribosomal subunits in eukaryotes?
60s large subunit and 40s small subunit- 80s when combined
What are the three sites of ribosome complex?
A- acceptor
P- peptidyl
E- exit
What are the steps involved in the initiation process of protein synthesis? Name the proteins involved
Met-tRNA is bound to GTP and loaded into the p site of the small subunit of the ribosome- other TF are added- (eIFs for euk and IFs for prok)- The large subunit will then bind and translation begins.
What are the steps involved in the elongation process of protein synthesis? Name the proteins involved and bonds formed
Aminoacyl tRNA is bound to a GTP elongation factor then loaded into the A site of ribosome. GTP hydrolysis and release of factor occur then peptidyl transferase will form a peptide bond between AA of a site and p site.
What are the steps involved in the termination process of protein synthesis? Name the proteins involved
RFs will recognize the stop codon at A site of ribosome and bind. Cleavage of the ester bond between the c terminus of peptide chain and tRNA. This releases the protein and GTP hydrolysis causes complex to disassociate.
polysomes
cluster of ribosomes that will translate a strand of mRNA simultaneously. Allows for increased protein production
What is the effect of streptomycin on protein synthesis?
Binds to the 30s subunit of prokaryotes to disrupt initiation- fmet-tRNA binding and association of 50s and 30s subunits
What is the effect of Tetracycline on protein synthesis?
Binds to the 30s subunit of prokaryotes to disrupt elongation- prevents entry of animoacyl tRNA to ribosome complex
What is the effect of Chloramphenicol on protein synthesis?
inhibits peptidyl transferase during elongation (prokaryotes)
What is the effect of clindamycin and erythromycin on protein synthesis?
binds to the large 50s subunit and prevents translocation of the ribosome during elongation
What is the effect of cyclohexamide on protein synthesis?
Inhibits peptidyl transferase in euks during elongation
What is the effect of diphtheria toxin on protein synthesis?
inactivates GTP bound eEF-2 interfering with ribosome translocation during elongation
What is the effect of Shiga Toxin and ricin on protein synthesis?
binds to large 60s subunit, blocking entry of aminoacyl tRNA to ribosome in elongation
What is the effect of puromycin on protein synthesis?
causes premature chain termination in both euks and proks- resembles the 3’ end of aminoacyl-tRNAs so added to the chain but causes the chain to be released when puromycylated chain formed.
What is the cytoplasmic pathway of protein sorting?
involves proteins destined for the cytoplasm, nucleus, peroxisome and mitochondria- synthesis begins/ends on free ribosomes and translocation signal will determine final destination
What is the secretory pathway of protein sorting?
involves proteins destined for the ER, secretion, lysosome and plasma membrane. synthesis begins with free protein but ends in the ER. Translocation signal will determine final destination
What is the translocation signal for the nucleus during protein sorting?
Lysine and Arginine rich signal- KKKRKRR
What is the translocation signal for the cytoplasm during protein sorting?
There is no translocation signal
What is the translocation signal for the peroxisome during protein sorting?
SKL signal- Serine, Lysine and Leucine
What is the translocation signal for the mitochondria during protein sorting?
N terminus hydrophobic alpha-helix signal- uses this to associate with chaperone proteins. Further sorting by TIM and TOM when at mitochondria
What is the translocation signal for the ER during protein sorting?
Starts originally with N terminus hydrophilic alpha helix signal then further sorting with KDEL signal
What is the translocation signal for the lysosome during protein sorting?
Starts originally with N terminus hydrophilic alpha helix signal then further sorting with mannose-6-phosphate
What is the translocation signal for the plasma membrane during protein sorting?
Starts originally with N terminus hydrophilic alpha helix signal then further sorting with N terminal a polar signal
What is the translocation signal for the secretion during protein sorting?
Starts originally with N terminus hydrophilic alpha helix signal then further sorting with tryptophan rich signal
What is I-cell disease?
A disorder that results from the protein that tags lysosome proteins with a mannose 6P being defective. The proteins will remain in the cytosol. Death a premature age
What is the difference between chaperones and chaperonions?
Chaperons assist in the folding of large proteins while chaperonions are barrel shape protein that help the folding of proteins using ATP hydrolysis.
What is acetylation?
The adding of an amine group to a protein on a lysine residue as a form of posttranslational modification
What is glycosylation?
Two types; O- glycosylation and N-glycosylation
O-glycosylation is the addition of a hydroxyl group to a serine
N-glycosylation is the addition of an amine group to Asn of Gln
What is a disulfide bond?
oxidation to achieve sulfide linkage of cysteine residues
What is phosphorylation?
Esterification of a hydroxyl group at Ser, Tyr or Thr
Alzheimer’s disease
amyloid precursor protein (APP) breaks down and forms amyloid beta peptide. This protein will then midfold and aggregate in the brain (extracellular). Misfolded proteins also result in the hyperphosphorylation of Tau resulting in cellular death (intracellular).
Parkinson’s disease
aggregation of alpha-synuclein form lewy bodies in dopaminergic cells in substantia nigra. Death of these cells and reduced levels of dopamine result.
Huntington’s disease
Mutation in the Huntingtin gene that results in CAG triplet repeats. There are polyglutamine repeats that result in midfolded proteins and aggregation. Cell death in the basal ganglia.
Crutzfeldt-Jacob disease
misfolding of prion proteins. The midfolded proteins result in cell death and a spongiform encephalopathies. Prions are also able to convert normal folded proteins to the prion form.
