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47 Cards in this Set
- Front
- Back
Where are polyribosomes located?
slide 5 |
free in the cytosol and attached to rough ER
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What is the destination of proteins made on the rough ER?
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secreted out of cell
part of cell membrane |
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Protein secretion is _______ and coordinated by _____
slide 7 |
Protein secretion is cotranslational and coordinated by SRP
SRP= signal recognition particle |
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What does the Signal recognition particle(SRP) do?
slide 7 |
SRP recognizes the signal peptide, temporarily blocks chain elongation by binding to P site, brings protein to ER by recognizing SRP receptor and elongation resumes extruded into the ER
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How does SRP recognize the signal peptide?
slide 7 |
protein has on Nterminus start AUG and then sequence of hydrophobic amino acids (approx 24)--> this is the signal that gets recognized by the SRP
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what are additional sequences that ship proteins to certain locations after being sent to the ER?
slide8 |
ER membrane - halt (stop-transfer) eg KDEL
Golgi apparatus membrane - unknown Plasma Membrane -default Secretion - default Lysosomal enzyme - mannose 6-phophate attachment |
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What is I-cell Disease caused by? and what does it cause?
slide 8 |
I cell disease (inclusion bodies in cells) is due to genetic defect in adding mannose 6-phosphate to the enzymes. This leads to failure of the enzyme to target lysosomes.
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Where do proteins get sent if they are made in the cytosol?
slide 9 |
Stay in Cytosol
Sent to Nucleus - have nuclear localization signal (basic) importins/RAN proteins Peroxizomes - peroxizomal targeting sequences / PTS receptors Mitochondria - N terminal leader (20-80 basic aa's) translocation complexes |
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Where are proteins that are sent to the nucleus made? What helps them to get there?
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The proteins are made in the cytosol
Have a nuclear localization signal (NLS) that is basic Imortins/ Ran proteins help bring them into the nucleus |
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Where do proteins that are shipped to the mitochondria get made?
slide 9 |
in the cytosol
Have an Nterminus (20-80 basic aa's) translocation complexes |
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What is Zellweger syndrome?
slide 9 |
genetic disease from mutations in genes required for peroxisome targeting or function
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What type of proteins does the mitochondria make itself?
slide 9 |
makes about 13 proteins chiefly of the electron transport chain. these are synthesized within the mitochondria
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Where do amino acid modifications occur?
slide 11 |
Occur on N AND C terminus and side chains of 15 amino acids
do NOT occur on gly,ala,val,ile, lue - because have unreactive side chains |
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What amino acids are not able to be modified and why?
slide 11 |
alanine
gylcine valine isoluecine luecine because they are aliphatic and have pretty unreactive side groups |
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Is amino acid modification reversible or irreversible?
slide 11 |
can be either just depends
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What roles does amino acid modification serve?
slide 11 |
Structural
Functional Regulatory |
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What are the implications for amino acid modification? Where could it help us to learn something?
slide 11 |
Pathology
Pharmocology Toxicology... |
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What does a perm do to your hair and how?
slide 12 |
It reorganizes the disulfide bridges.
Keratin in human hair is 14% cysteine Disulfide bridges here create the protein structure leading to the type of hair you have. you oxidize the hair to make new dissulfide bonds. |
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what is phosphorylation frequently used for?
slide 14 |
used to control enzyme activity
- usually on Ser, thy or tyr (hydroxyl containing groups) catalyzed by kinases using ATP reversible phosphotase action can increase or decrease activity |
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what are the results of phosphorylating translation initiation factors
eIF2 eIF4E 4E-BP slide 14 |
eIF2 - inhibit
eIF4E - Stiumulate 4E-BP stimulatory (derepression) ie. indirectly stimulates by deactivating something else |
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Functional aspects of post translational modificiations
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1. Genetic Dieases - MSD
2. Nutrition - Se and SeCys 3. Anticoagulants - vitamin K and warfarin (coumadin) 4. Diabetes mellitus - protein glycation |
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Mutliple Sulfatase Deficiency (MSD)
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progressive paralysis, skeletal deformities, neurological defects.
Infants develop slowly, lose abilities at 1 Combinees the enzyme deficiency and phenotypic features of several diseases |
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What is the molecular basis of MSD
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Increased accumulation of mucopolysaccarides (heparan sulfate, dermatan sulfate) and other sulfates (cholesterol sulfate)
Defect in cysteine oxidation common to all sulfatases Primary defect is in sulfatase-modifying factor-1 gene (SMF-1) sulfatases cannot be converted to 2-amino-3oxopropionic acid |
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What is selenium?
What are the ramifications of having a diet where you do not get enough selenium? |
Selenium is an essential micronutrient
Lack of selenium leads to dilated cardiomyopathy, congestive heart failure, striated muscle degeneration, weakenes (AKA Keshan disease) |
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What is Keshan disease caused by and what are its symptoms?
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caused by lack of selenium
leads to cardiomyopathy, congestive heart failure, flabby heart |
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Why do we need selenium?
slide 18 |
because it is an essential part of a small number of proteins (about 25)
most selenoproteins catalyze oxido-reduction reactions |
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What do selenoproteins do? And an example.
slide 18 |
they catalyze oxido-reduction reactions
ex. Gluthione peroxidase 5'-delodinases (T4--->T3) |
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What does a Gluthione Peroxidase do?
slide 19 |
Destroys reactive damaging H2O2
Reduces organic peroxides (R-OOH to R-OH) uses Gluthiathione (G-SH) as a reducing agent Glutathione is oxidized and peroxide is reduced |
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where is glutamate attached to G-SH glutathione?
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one the gamma carbon
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What is used to convert dietary idodide to activated iodine [I]ox?
slide 20 |
H2O2 thyroperoxidase
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What is more active T4 or T3?
slide 20 |
T3
T4 is thyroxine which has an extra iodine molecule that must be cleaved to form T3 |
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What are the steps to processing iodine to be a functional thyroid hormone?
slide 20 |
1. Dietary iodide with the help of thyroperoxidase is converted to activated Iodine [I]ox
2. Iodinates tyrosine residue in thyroglobulin tyr--->mono and di-iodotyrosine (MIT and DIT) 3. MIT + DIT ---> T3 thyroxine chain DIT + DIT ----> T4 5. T4--->T3 more active catalyzed by 5' deiodinease |
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what is the reaction to convert T4 to T3 catalyzed by?
slide 20 |
5' deiodinase
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What is goiter caused by?
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5' deiodinase deficiency
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When is Selenium incorporated into a protein?
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Cotranslatinally, ie, at the time of translation
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How is a selenocysteine incorporated into a protein?
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considered to be the 21 amino acid.
Uses a modified UGA codon (usually a stop codon. Later will have a UAA codon and after in the 3' UTR will have SECIS element which helps the cell to recognize that the UGA codon should be the SeCys and not a stop |
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Where and how is selenium attached to protein?
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Attached to a Ser-tRNA residue by HSePo3^-2 using ATP
becomes SeCys-tRNA The selenocysteine tRNAs are initially charged with serine by seryl-tRNA ligase, but the resulting Ser-tRNA(Sec) is not used for translation because it is not recognised by the normal translation factor (EF-Tu in bacteria, EF1-alpha in eukaryotes). Rather, the tRNA-bound seryl residue is converted to a selenocysteyl-residue by the pyridoxal phosphate-containing enzyme selenocysteine synthase. Finally, the resulting Sec-tRNA(Sec) is specifically bound to an alternative translational elongation factor (SelB or mSelB) which delivers it in a targeted manner to the ribosomes translating mRNAs for selenoproteins. |
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What is vitamin K essential for?
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koagulatin
Vitamin K mediates gamma-carboxlation |
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What is selenocystein? selenoprotein?
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Selenocysteine has a structure similar to cysteine, but with an atom of selenium taking the place of the usual sulfur.
Proteins that contain one or more selenocysteine residues are called selenoproteins. |
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What happens when the SEICS element is deleted in translation of a selenoprotein?
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the UGA that is normally used in this instance to code for the selenocysteine instead is read as a stop codon and the protein is truncated
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What reaction does vitamin K mediate?
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Gamma carboxylation
is a post translational modification where an additional carboxyl is attached to gamma carbon of Glutamate |
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What is Vitamin K / cogulation inhibited by?
slide 22 |
Coumadin
warfarin - used as toxin for rats |
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How can you get a false low AIC?
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reb blood cells die early.
Can be caused by sickle cell disease, or drugs that cause RBCs to die early |
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Does glycosylation affect the function of RBC?
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nope but can affect other proteins in the body
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How does glycosylation of RBC occur?
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occurs spontaneously, not catalyzed by anything
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what is AGE?
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advanced glycosylated endproducts,
caused by gyoslyation of proteins |
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How could you get a false high AIC?
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RBC live longer than expected. Could be caused by someone who lacks a spleen - this is where RBC go to die
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