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11 Cards in this Set
- Front
- Back
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General expression for ligand binding |
P + L ⇋P·L Kd P = Protein L = Ligand (unbound) · = non-covalent interaction |
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Kd |
[P][L]/[P·L] |
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θ |
Fraction of occupied binding sites [occupied]/[total] θ = [P·L]/([P·L]+[P]) = [L]/([L]+[Kd]) |
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At what [L] or pGas will θ = 0.5? |
[L] = Kd pGas = Kd |
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Smaller Kd means |
Higher affinity, tighter binding |
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Larger Kd means |
Lower affinity, looser binding |
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Myoglobin |
-Mb -1 polypeptide chain w/8 a-helicies labeled A-H -1 heme group -O2 binds to Fe in heme and HisE7 (invariant) in protein -O2 storage b/c high affinity -hyperbolic binding curve |
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θ for gasses |
θ = pGas/(pGas + Kd) |
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Hemoglobin |
-4 subunits -heme group -sigmoidal binding curve -High affinity for O2 in lungs (R state), low affinity in tissue (T state) -cooperative binding |
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Cooperative binding |
Binding one ligand increases affinity for other ligands |
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Generalized binding curve |
[L]^n/([L]^n+Kd), 1<= n <= N Limitations: -1 L & 1 binding site (N=1,n=1) ->1 L & independent binding (N>1,n=1) ->1 ligand and cooperative binding (N>1) |
