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Related Flashcards
Cards In This Set
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What are the 6 types of post-translational modification (PTM)?
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1) Proteolysis2) Adding carbohydrates3) Prenylation & adding other lipids4) Ubiquitylation, adding small proteins5) Phosphorylation/methylation/acetylation/etc6) Unique amino acid modification
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What is the PTM mechanism for insulin?
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Mature insulin has A and B chains; immature insulin connects A and B with a C chain that allows correct disulfide bonding between A & B; C is then cleaved since it prevents binding to IR.
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What is the PTM mechanism for Collagen?
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Proproteins have both N and C terminal propeptides that are necessary for assembly of coiled coil. Need to be cleaved to allow for stacking/aggregation into fibrils.
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What is a lipid anchor? What groups are involved?
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Globular proteins attached to lipid bilayer @ site of activity.
Inner leaflet:1) Isoprenoid (farnesyl [C15]; geranylgeranyl [C20])2) Fatty Acyl (Myristic acid [C14]; palmitic acid [C16]) Outer leaflet:3) Glycophosphatidylinositol |
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How is Ras regulated?
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1) farnesylation2) carboxymethylation3) Palmitoylation - cycles Ras from membrane to Golgi
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How does a farnesyltransferase inhibitor (FTI) inhibit Ras activity?
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Farnesyltransferase must recognize CaaX sequence on Ras; FTIs bind to Caax motif and prevent farnesylation of Ras. This prevents Ras from being localized correctly.-Unfortunately the cell can get around this by adding geranylgeranyl group, etc
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Cholera, diptheria, and pertussis toxins rely on which type of PTM?
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ADP-ribosylation
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What are the 5 roles of glycosylation?
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1) Aids protein folding2) Increase protein's aqueous solubility3) Increase/decrease stability by protecting from or signaling to protease4) Signal localization5) Lubricant/shock absorber
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What are glycoforms?
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Forms of the same protein with various carbohydrate groups
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N-linked glycosylation:-Adds to which amino acid residue?-When does modification occur?-What is the recognition sequence?-Which carrier molecule facilitates transfer?-Where does the protein go for final sugar processing?
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-Adds charged sugars to Asparagine residues-Occurs Co-Translationally (into ER lumen)- N-X-S/T recognition sequence (X not proline)-dolichol phosphate-Golgi body
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Which proteins facilitate folding of N-linked glycosylated proteins?
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calnexin/calreticulin chaperone system
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O-linked glycosylation:-When and where does it occur?-How does it differ from N-linked?
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-Post-translational, fully folded -exclusively in Golgi body
-Sugars added one by one-No specific recognition sequence (rich in S/T), recognizes structural motif |
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What is the function of a lysosome?What step needs to occur before this function?
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-Degradation of glycoproteins & glycoconjucates (ordered, by glycosidases)-Removal of sugars
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What is a glycosaminoglycan?
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Long unbranched polysaccharide - many disaccharide units.-often uronic acid & hexosamine
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What is the function of Aggrecan?
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Main proteoglycan of cartilage: contributes resiliency due to bottlebrush structure. Highly hydrated; can be compressed and spring back due to neg charge repulsion.-Allows elasticity of vertebrate joints.
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