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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
• 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
• 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
• 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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- Spring '08