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42 Cards in this Set
- Front
- Back
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What is co-translational translocation?
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when proteins are synthesized across membrane into rough ER for further modifications
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What synthesizes proteins that are released into the cytoplasm?
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free ribosomes
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Proteins synthesized by bound ribosome of the rough ER cross into ER for what?
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further modifications
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What is it called when Signal Recognition Protein (SRP) targets proteins for ER?
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Targeting
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Proteins synthesized in the cytosol are transported where for further modification?
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into lumen of ER
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Secreted proteins are synthesized by what?
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ribosomes on surface of ER
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What is present of the N-terminus that signals the protein to cross a membrane?
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Signal peptide
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What are 16-30 residues long, and include 4-15 hydrophobic residues?
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Signal peptides
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The ribosome binds to _______, and the signal peptide is inserted thru a pore in the membrane.
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ribophorin
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SRP binds to ________ as it emerges from the ribosome. Translation is inhibited.
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the signal peptide
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SRP binds to the SRP receptor where in the cell?
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on surface of ER
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What removes the signal peptide from the polypeptide?
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signal peptidase
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What happens as soon as peptide exits the ribosome?
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Folding
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What assists in folding of the proteins?
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Chaperones (helper proteins)
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Misfolded proteins are tagged for destruction by what?
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proteases
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What binds to hydrophobic regions of extended (unfolded) polypeptides?
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Hsp70
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What is an Hsp60 E.Coli chaperonin?
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GroES-GroEL
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What is a signal transduction protein chaperone?
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Hsp90
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Rhodanese needs how many ATP to completely fold one copy?
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130 ATP
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What is the eukaryotes equivalent of GroES-GroEL?
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TCP-1 ring complex
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Eukaryotic proteins are degraded by what?
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lysosomes or proteosomes
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Eukaryotic proteins are targeted for proteosome destruction by what?
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ubiquitination
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What is the core structure of a proteosome?
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cylindrical stable of a7B7B7a7 subunits
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What part of the proteosome selects ubiquinated proteins for degradation in the core cavity?
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Cap Structures
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Ubiquitin is attached to selected proteins via isopeptide bonds formed between what?
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Ubiquitin Carboxy-terminus and
Free amino group on protein |
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What if there are NO free amino groups on your protein for ubiquitin?
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use something else for protein degradation. proteins with acidic N-termini show a tRNA requirement for degradation. Arg-tRNA arg is a protein transferase
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Improperly folded proteins are tagged by the protein _______ for degradation by the proteosome.
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ubiquitin
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Recently, Ubiquination was revealed to not only aid in destruction of protein but what else?
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form of REGULATION
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What are 2 examples of post-translational amino acid modifications?
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glycosylation and phosphorylation
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What is the most common form of post-translational processing?
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Proteolytic cleavage
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Reversible post-translational modification allow for regulation of protein function. Give an example.
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Phosphorylation is a reversible one. Ex. include proteolysis, removal of N-terminal methionine and removal of a peptide
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Why are there very few disulfide bonds in cytoplasmic proteins?
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cytoplasm is usually a reducing environment with lots of reducing compounds around
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Transfer of a carbon chain from a phosphate to the thiol group of a cysteine on the protein is an example of what?
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Farnesylation (Ras and Farnesyl pyrophosphate used)
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Where on the protein do you typically have phosphorylation?
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Ser, Thr, Tyr
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Where on the protein do you typically have hydroxylation?
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Pro (collagen)
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Where on the protein do you typically have glycosylation?
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Asn (Mannose)
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Where on the protein do you typically have metal cofactors?
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Cys, His, Glu (four cysteins-Zn)
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What may make up to 80% of the mass of the glycoprotein?
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carbohydrates
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A common _______reaction is the covalent attachment of a complex oligosaccharide to the side chain of an asparagine residue.
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glycosylation
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What is a lipid embedded in the ER membrane?
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Dolichol
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What do humans lack that gives us protection from malaria species but make us more suspectible to rheumatoid arthritis and asthma?
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Sialic Acid
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What is the malarial parasite that has been a major selective pressure in human evolution?
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Plasmodium
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