Protein Structure Flashcards
What are the properties of a peptide bond?
partial double bond character; dipole moment, trans-configuration, uncharged but polar, rigid and planar
What is the geometry of a peptide bond?
planar trans configuration
native conformation
the tertiary structure of a protein
bends
beta-bends are seen in beta-sheets. They function to reverse the direction of the polypeptide chain; usually composed of 4 AA
What is primary structure of a protein?
amino acid residues
What is secondary structure of a protein?
3-dimensional shape
What is tertiary structure of a protein?
folding of 3-dimensional structure within the same polypeptide
What is quaternary structure of a protein?
assembly of multiple polypeptides
Compare alpha helix and beta helix
Alpha: helical, 3.6 residues/turn, intrachain H-bonding;
Beta: pleated, all peptides involved in H-bonding; parallel or anti-parallel
Define supersecondary structure
folding of secondary structure into small, discrete, commonly-observed aggregates of secondary structure
examples:
beta-alpha-beta loop
alpha-alpha corner
beta-barrel
genetic disease results from abnormalities in this structure of a protein
Primary structure
Intramolecular disulfide bridge vs Intermolecular disulfide bridge
intramolecular is between cysteines on same polypeptide; intermolecular is between cycteines on different polypeptides
What process can be used to break peptide bonds?
Acid hydrolysis
What reagent is used in sequencing of peptides and what is its function?
Phenyisothiocynate (Edman’s reagent); it labels the N-ternminal amino, which weakens the peptide bond between the first and second amino.
What stabilizes the secondary structure of a protein?
H-bonds
