Spectroscopic, calorimetric, and kinetic demonstration of conformational adaptation in peptide-antibody recognition.

作者: Lukas Leder , Christine Berger , Susanne Bornhauser , Hans Wendt , Friederike Ackermann

DOI: 10.1021/BI00050A035

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摘要: Little is known about the extent to which protein flexibility contributes antigen-antibody recognition and cross-reactivity. Using short coil peptides (leucine zippers) as model antigens, we demonstrate that a monoclonal antibody can force noncognate peptide into conformation similar of cognate against directed. Monoclonal antibodies 29AB 13AD were raised 29-residue LZ (Ac-EYEALEKKLAALEAKLQALEKKLEALEHG-amide) forms very stable coiled coil. The two cross-reacted strongly with random analogue LZ(7P14P) contains Lys-->Pro Ala-->Pro substitutions in positions 7 14, respectively. antibody-bound adopted an altered possibly was coil-like, shown by CD difference spectroscopy fluorescence quenching experiments on coumarin-labeled peptides. Isothermal titration calorimetry revealed cross-reaction exhibited large unfavorable entropy. This, however, compensated more favorable enthalpy, resulting only small between association constants for LZ(7P14P), To investigate opposite type cross-reaction, 42PF LZ(7P14P). forcing it dissociate single chains. Enthalpy/entropy compensation again enabled now entropically favored enthalpically disfavored. rate reaction controlled dissociation This observation, well generally much slower peptides, indicated cross-reactivity occurred because selected conformer antigen binds strongest, mechanism call "induced fit conformational selection."

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