pH Dependence of Antibody/Lysozyme Complexation
Received January 28, 1997 Revised Manuscript Received August 19, 1997 Abstract: Association between proteins often depends on the pH and ionic
strength conditions of the
medium in which it takes place. This is especially true in
complexation involving titratable residues at
the complex interface. Continuum electrostatics methods were used
to calculate the pH-dependent
energetics of association of hen egg lysozyme with two closely related
monoclonal antibodies raised
against it and the association of these antibodies against an avian
species variant. A detailed analysis of
the energetic contributions reveals that even though the hallmark of
association in the two complexes is
the presence of conserved charged-residue interactions, the environment
of these interactions significantly
influences the titration behavior and concomitantly the energetics.
The contributing factors include minor
structural rearrangements, buried interfacial area, dielectric
environment of the key titratable residues,
and geometry of the residue dispositions. Modeled structures of
several mutant complexes were also
studied so as to further delineate the contribution of individual
factors to the titration behavior.
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