Protein Interactions - Hori Flashcards
Describe the action of Lispro
In insulin-dependent type I diabetes patients, Lispro is used as an insulin analog, where the amino acid residues lysine and proline are switched in their positions from the normal endogenous insulin positions. Insulin, a hexamer, can only be absorbed as it breaks down from a hexamer, to a dimer, and then to a monomer. Lispro presents itself as an insulin analog that is in a primarily monomeric form. Thus, it can be absorbed more easily.
What is Kd for a protein, and what does it mean?
Dissociation constant of a protein complex. Kd = [P][A]/[PA]. It indicates how much a protein will dissociate in solution. Lower Kd = higher affinity
Difference between specificity and affinity
Specificity: What kind of ligands the protein allows to bind
Affinity: How willing a protein is to bind a ligand
Langmuir Isotherm
Describes the action of ligand-protein binding per protein molecule. r vs. [A]
r = [A] / (Kd + [A])
Scatchard plot
Linear representation of langmuir (r/[A] vs. r)
What do you do with more binding sites?
r = n[A]/(Kd +[A])…add n to Langmuir
For multiple binding sites in a scatchard, x-intercept = n
What does equilibrium dialysis allow you to do?
Determine # of binding sites for ligands
What are two more complicated ligand-protein situations?
- Single protein with sites of differing affinities
2. Proteins with affinities that depend on ligand concentration
Describe cooperativity
Positive: First event will make second event happen more quickly (sharper curve to saturation)
Negative: Initial events are making later ones more difficult to occur (more shallow curve to binding sites)
Must have multiple sites
Why would Mb reach saturation at a much lower pressure than Hb?
Mb is an O2 storage molecule, so would need to store more O2
Hb is simply transporting
What is YO2?
Fractional saturation of Mb by O2 (replaces r in Scatchard)
What is p50? How does it relate to Kd?
pO2 at which YO2 = 0.5…Kd=p50
