The Human Cytomegalovirus Fc Receptor gp68 Binds the Fc CH2 ...

Characterization of Binding of HCMV gp68 to Fc
of primary amine-coupled hdFc) are shown in black. Fits for a bivalent ligand binding model,
which assumes two independent binding sites on Fcγ, and for a single site binding model, are
shown as blue lines, and affinities are indicated with K D1 and K D2 corresponding to the first and
second binding events, respectively, for the bivalent ligand model. Residuals are shown below
each fit. (C) Equilibrium binding response for hdFc injected over gp68 (68-289) at pH 8.1
(triangles) or pH 6.0 (squares) are shown at various injection concentrations. Data are plotted as
percent binding at equilibrium (normalized for maximal binding) for each injection of hdFc and
fit to a single-binding site isotherm. The derived K D s are 60 nM at pH 6.0 and 300 nM at pH 8.1.
Four independent determinations of the K D at either pH 7.8 or 8.1 ranged from 85 nM to 300 nM;
thus, the affinity of gp68 binding to Fc is similar, or even slightly tighter, at pH 6.0 as compared
to pH 8.1.
ACCEPTED
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