LECTURE 3 - Binding p 116 - 126 Protein + Ligand...

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Unformatted text preview: Binding p 116 - 126 Protein + Ligand Protein-Ligand Complex Dissociation constant = K d K d = [ P ][ L ] [ PL ]- the smaller the K d , the tighter the binding Binding Protein + Ligand Protein-Ligand Complex Occupancy = = binding _ sites _ occupied binding _ sites _ total = [ PL ] [ PL ] + [ P ] = [ L ] [ L ] + K d p 116 - 126 Binding Protein + Ligand Protein-Ligand Complex Occupancy = = binding _ sites _ occupied binding _ sites _ total = [ PL ] [ PL ] + [ P ] = [ L ] [ L ] + K d p 116 - 126 Myoglobin p 116 - 126 Fe 2+ Myoglobin p 116 - 126 K d Myoglobin and Hemoglobin p 116 - 126 Hemoglobin: a heterotetramer ( 2 2 ) Hemoglobin p 116 - 126 Sigmoidal binding curve = diagnostic for cooperativity 1st O 2 makes 2nd O 2 bind tighter, which makes 3rd O 2 bind even tighter, which makes last O 2 bind tightest pseudoglobin = 0.79 - 0.54 = 0.25 myoglobin = 0.97 - 0.91 = 0.06 hemoglobin = 0.95 - 0.55 = 0.4 Hemoglobin p 116 - 126 It all starts with a 0.6 shift .leading to knob into hole shift Hemoglobin p 116 - 126 Hemoglobin p 116 - 126 Hemoglobin p 116 - 126 Bohr Effect: Binding of H + and CO 2 is inversely related to binding by O 2 :- at low pH (= high [H + ]) and high CO 2 in peripheral tissues, O 2 afFnity decreases- in lungs, as CO 2 is excreted and the blood pH rises, afFnity for O 2 increases-Mechanism: stabilize T-state at low pH Hemoglobin p 116 - 126 BPG: bisphosphoglycerate: Fetal hemoglobin binds BPG less tightly: fetus can steal oxygen from mother At altitude, you make more BPG: more efcient release of oxygen into tissue O P O O O O O O P O O O Hemoglobin p 116 - 126 normal sickle cell Single amino acid substitution: Glu60Val Sickle cell anemia: a misfolding disease Hemoglobin p 116 - 126 Hemoglobin...
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LECTURE 3 - Binding p 116 - 126 Protein + Ligand...

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