cooperativity ligand effector homotropic effector

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Unformatted text preview: Terminology: fractional saturation, prosthetic group, apoprotein, holoprotein, protomer, binding site, allosteric (site, effector, protein...), cooperativity, ligand, effector, homotropic effector (modulator), heterotropic effector (modulator) •  Describe the globin fold, explain how the helices are designated, and the roles of proximal and distal His residues in binding of heme and of O2. •  Write the dissociation equilibrium of a protein-ligand complex P•L as a chemical reaction and the expression for Kd. •  Relate magnitude of Kd to binding affinity (tightness) •  Understand θ (fractional saturation) and its relationship to concentrations of occupied and empty binding sites on proteins. Learning Objectives L17-L20, continued •  Write the equation relating θ to [ligand] for noncooperative ligand binding in terms of [ligand] and Kd, and in terms of pO2 and P50. Sketch a plot of θ vs. [ligand] for noncooperative ligand binding and identify Kd on such a plot. •  Describe how and where O2 binds in the structure of Mb and Hb, including roles of protein functional groups and heme, and the oxidation state of heme Fe required for O2 binding. •  Describe/sketch a binding curve that shows cooperativity (cooperative ligand binding). In what part of the curve (what part of the [ligand] concentration range) is the protein predominantly in the conformation with low ligand binding affinity, and in what part of the ligand concentration range is the predominant form the high binding affinity conformation? Learning Objectives L17-L20, continued •  Explain how Hb works physiologically (in vivo), i.e., how cooperativity in O2 binding facilitates...
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