Protein Structure/Folding Flashcards
Destabilizing folding factors
Chain entropy and unfavorable reactions
Stabilizing folding factors
Increasing Van der Waals, hydrogen bonds, hydrophobic interactions, disulfide bridges
Define melting point (Tm)
Temperature at which 50% of the protein is denatured
Define denaturing point (Cm)
Concentration at which 50% of the protein is denatured
How are disulfide bonds formed?
2 redox reactions between 2 cysteins
Characteristics of a right handed a-helix
3.6 residues per turn; stabilized by H-bonds; III quadrant of Ramachandran plot
Characteristics of a B-pleated sheet
Stabilized by H-bonds; allows for dense packing; parallel or anti-parallel; R-groups on outside (above/below sheet); in quadrant I on Ramachandran plot
Characteristics of a B-turn
4 amino acids; H-bonding (i+3)
Type 1 = proline
Type 2 = glycine
Define Co-factors with example
Non-protein molecules/ions required for enzymatic activity
Ex: Mg2+
Define prosthetic group and give example
Co-factor that is an integral part of the structure; may or may not be covalently bound
Ex: heme in myoglobin
Characteristics of Hemoglobin
2 alpha and 2 beta chains each with Heme, each Heme with Fe2+
The heme is not covalently attached
Exhibits cooperativity - shifts between R state and L state
Define the R-state of hemoglobin and how it shifts
Favored when oxygen is bound and has high affinity for O2
O2 binding causes conformational change in quaternary structure, making the next O2 more favorable to bind
Define the L-state of hemoglobin and how it shifts
Favored when O2 concentrations are low
Has a low affinity for O2
Shifts to R-state when O2 binds b/c shift in quaternary structure increases O2 affinity for other sites
Characteristics of Sickle-Cell Anemia
B-chain mutation in hemoglobin (Glu
