MBOD - Three dimensional structure of proteins

  1. What is the secondary structure of a protein?
    • The organization of primary structural features.
    • Alpha helices and beta sheets
  2. What is the tertiary structure of a protein?
    Steric relationships of AA's that may be far apart in AA sequence
  3. What is quaternary structure of a protein?
    Mode of association between two or more polypeptide chains
  4. How are the six atoms in an AA oriented?
    Coplanar. This is due to resonance.
  5. Does the alpha carbon in a peptide bond lie cis or trans to a C-N bond?
  6. What is the vertical rise for each AA residue in an alpha helix?
    • 1.5 angstroms.
    • There are 3.6 resudes per turn.
    • Each residue gives 100 degrees of separation.
  7. What is an alpha helix stabalized by?
    Hydrogen bonds between carboxyl and amino groups
  8. What is a very common "open" motif that can have parallel or antiparallel configurations, and is stabilized by hydrogen bonding?
    Beta sheet
  9. What residues favor formation of alpha helix?
    Met, Glu, Leu, Ala, Gln
  10. Which residues favor formation of beta sheets?
    Val, Ile, Phe, Tyr
  11. In a membrane integral protein that forms a water pore, where would charged residues be found? Where would hydrophobic residues be found?
    • Charged - in the center of the pore
    • Hydrophobic - on the outside of the pore
  12. How can water soluble enzymes be associated with membranes?
    Post translational modifications with hydrophobic groups
  13. Whis is a disulfide bridge?
    • Oxidative cross binding of cysteine residues.
    • Sulfhydryl groups giving up electrons (H) to bind to another sulfhydryl group that has lost an electron
  14. Describe the residues of intrinsically unstructured proteins.
    Many charged residues. Also very polar.
  15. What does PDI do?
    Catalyzes disulfide exchange reactions
  16. What does PPI do?
    Catalyzes interconversion of cis to trans configuration in peptide bonds. (Trans is normal)
  17. What do molecular chaperones do?
    Bind to hydrophobic portions of a protein and keep them from aggregating and folding.
  18. What is a contiguous portion of a polypeptide chain that folds independently into 3d structures?
  19. What does Cystic Fibrosis result from?
    F508X mutation in CFTR. This results in improper folding of chloride transport protein.
Card Set
MBOD - Three dimensional structure of proteins
MBOD - Three dimensional protein structures