4 Protein Targeting

  1. the two classes of ribosomes are:
    cytosolic ribosomes, RER-associated polyribosomes; classification based on site of protein synthesis
  2. all ribosomes are:
    chemically identical
  3. proteins produced by cytosolic ribosomes can go to the (4):
    • 1) cytosol
    • 2) mitochondria
    • 3) nucleus
    • 4) peroxisomes
  4. proteins produced by RER ribosomes can go to the:
    1) stay in the ER 2) be secreted (secretory vesicles) 3) Golgi 4) lysosome 4) plasma membrane
  5. signal peptide/signal sequence
    the first two dozen amino acids of a protein that specify which part of the cell the protein is going to; the signal is located on a protein's N-terminus, or 5' end, the end that's synthesized first
  6. What is the targeting sequence for the nucleus?
    5-7 basic amino acids (small)
  7. What is the targeting sequence that moves translation from the cytoplasm to the ER?
    20-25 hydrophobic amino acids at the N-terminus; happens DURING translation, ribosome mRNA complex subsequently moves to ER & docks
  8. What is the targeting sequence for the peroxisome?
    SKL (tri-peptide serene lysine leucine); located on the C-terminus; a defect in SKL means the peroxisome won't have proteins to degrade 'toxins'
  9. What targeting sequence means a protein belongs in the endoplasmic recticulum?
    KDEL (tetra peptide sequence); used to retrieves proteins that try to escape from ER
  10. What is the targeting sequence for the lysosome?
    mannose-6-phosphate; mannose 6-phosphate kinase adds phosphate to 6th position on a mannose sugar in the protein
  11. Chaperone Proteins
    proteins that complex with nascent polypeptides & if they sense they're folded properly, direct them to their destination
  12. Where will a chaperone protein take a nascent protein if it's been folded incorrectly?
    the proteosome
  13. Peroxisome
    organelles that break down oxidative products, detoxify cells, and contain enzymes that destroy free radicals
  14. Peroxisomal Targeting Diseases
    • 1) Zellweger Syndrome
    • 2) NALD (neonatal adrenoleukodystrophy)
  15. The inside of the ER is topologically equivalent to:
    the OUTSIDE of the cell
  16. Golgi
    packages proteins inside the cell before they are sent to their destination; cis golgi = near nucleus; trans golgo = farther from nucleus
  17. Know the Order of Golgi Events:
    1) goes from the ER to the Golgi; in the ER proteins have been translated, sorted, and have had initial sugar additions

    2) cis golgi network: phosphorylation & sorting

    3) cis cisterna: trim sugars, more sorting

    4) medial cistern: trim sugars, add sugars, & SORT

    5) trans cistern: add sugars, sorting

    6) trans golgi network: process proteins, sort

    • send vesicles to one of 3 places:
    • 1) lysosome
    • 2) plasma membrane
    • 3) secretory vesicles
  18. Golgi sends vesicles to one of 3 places:
    • 1) lysosome
    • 2) plasma membrane
    • 3) secretory vesicles
  19. Lysosome
    organelles with acid hydrolase enzymes that break down waste materials and cellular debris; enzymes work best at low pH achieved by H+ ATPase pump in lysosome membrane (ph = 5)
  20. Diseases that can be treated with enzyme replacement therapy (3):
    • 1) Hunter's
    • 2) Fabry's
    • 3) Goucher's
  21. I-Cell Diseases (Inclusion-cell)
    proteins are not properly targeted for lysosome in the Golgi; M6P signal is missing; end up being secreted; build up of substances in lysosomes because there's no enzyme to degrade them
  22. Huntington Disease
    another protein targeting disease: cytoplasmic proteins accumulate in nucleus because of mutation that creates NLS signal
  23. LSDs (11 on slide:
    • I-Cell
    • Tay-Sachs
    • Fabry
    • Gaucher
    • Pompe
    • Gangliosidoses
    • Mucopolysaccharidoses
    •   -Hurler's
    •   -Pseudo-Hurler's
    •   -Hunter
    •   -Sanfilippo
    •   -Morquio
    • Sulfatase deficiencies
    • Beta-Galactosidase (enzyme) deficiencies
    • *Niemann-Pick
  24. Gangliosidosis
    lipid storage disorder caused by the accumulation of gangliosides, a TYPE of sphingolipid
Card Set
4 Protein Targeting
Cell Biology Exam 1