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Domain interactions in antibody Fv and scFv fragments: effects on unfolding kinetics and equilibria
Author(s) -
Jäger Marcus,
Plückthun Andreas
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01532-x
Subject(s) - chemistry , kinetics , equilibrium unfolding , biophysics , dissociation (chemistry) , denaturation (fissile materials) , crystallography , protein folding , biochemistry , biology , physics , quantum mechanics , nuclear chemistry
The equilibrium denaturation and unfolding kinetics of the domains V L and V H have been compared with those of the Fv and single‐chain Fv (scFv) fragment of an engineered variant of the antibody McPC603 in the presence and absence of the antigen phosphorylcholine. The scFv fragment is significantly more stable than the isolated constituting domains. Antigen binding stabilizes the heterodimeric assembly even further. Domain dissociation and domain unfolding are coupled processes, giving rise to a highly cooperative unfolding transition. For the Fv fragment, cooperative unfolding is only observed in the presence of antigen. At low protein concentrations and in the absence of antigen, the Fv fragment is significantly destabilized, leading to quantitative domain dissociation before significant domain unfolding takes place. The kinetic unfolding of V H , V L and the scFv fragment is monophasic. Unfolding of the scFv fragment is much slower, when extrapolated to zero denaturant, than either of the isolated domains, suggesting that the higher thermodynamic stability of the scFv fragment is at least partially due to a high‐energy transition state for unfolding. These studies emphasize the enormous importance of mutual domain stabilization in engineering stable antibodies.