Protein Structure
Interacting surfaces
tertiary structure.
True or false. To take a polypeptide chain and fold it into the three dimensional structure of a protein requires elaborate machinery which behaves as a cellular erector set taking a polypeptide chain and folding it into its final state.
False. All that is required for a polypeptide chain to fold into its native three dimensional structure is its interaction with an aqueous environment
True or false. Most side chains are not compatible with an α-helix.
False. Most side chains are compatible with an α-helix because they project away from the helix-center.
True or false. Molecules of the peptide bond are free to rotate.
False. Rotation about the peptide bond does not normally occur.
True or false. The sections of the β pleated sheet are capable of running on in parallel directions.
False. Sections of the β pleated sheet are capable of running an a parallel or anti-parallel direction.
True or false. The reverse (tight, β) turns is often initiated by methionine.
False. The reverse (tight, β) turns is often initiated by proline.
True or false. The peptide group of a peptide bond have two permanent dipoles aligned in opposite directions.
False. The two permanent dipoles align in the same direction
What is the major thermodynamic driving force of protein folding?
The hydrophobic effect.
True or False. Analysis of primary structure of proteins has given insight into the molecular basis of disease.
True
True or false. An amino acid critical for the function of a protein is likely to be conserved when comparing sequences for the same protein in two evolutionarily distant organisms?
True.
True or false. Other bonds in the polypeptide backbone are free to rotate.
True.
True or false. Peptide bond has partial double bond character due to resonance stabilization.
True.
True or false. The hydrogen bonding that stabilizes the β pleated sheet is an example of tertiary structure.
True.
True or false. The α-helix is extensively stabilized by hydrogen bonds within the unit of structure
True.
How is a hydrophobic surface created on a α-helical structure?
alternate inserting hydrophobic residues every 3rd and then 4th position in the polypeptide chain.
structure of peptide bond
carbonyl and oxygen amide hydrogen are in opposite alignment in a trans configuration
What is the function of the reverse (tight, β) turn?
causes the polypeptide chain to reverse direction allowing other forms of secondary structure to fold and pack on one another
α-helix
commonly occurring secondary structure. right-handed helix wound around a central axis
tertiary structure
how segments of secondary structure fold and pack to form a complete three dimensional structure of the protein
primary structure
linear sequence of amino acids in the polypeptide chain.
quaternary structure
non-covalnet assembly of polypeptide chains
In what kind of proteins are quaternary structures found?
oligomeric proteins with more than one polypeptide chain
What does proline do to an α-helix
proline is a helix breaking or kinking amino acid.
homopolymer
quaternary structure that consists of a single protein subunit
heteropolymer
quaternary structure that consists of different protein subunits.
What are interacting surfaces a consequence of?
secondary structure allows for the segregation of side chain functional groups to different surfaces of a structure.
Reverse (tight, β) turns
secondary structure often found in globular proteins.
Random structure
secondary structure that lacks a defined repeating geometrical pattern.
β (pleated) sheet
secondary structure with extended conformation. characteristic zig-zag pattern with side chains above and below the horizontal axis.
secondary structure
short segments of the polypeptide backbone that assume distinct structures
Denaturation
the partial or complete unfolding of a protein resulting in the loss of function.
What dictates a protein's 3-D structure and function?
the primary structure
