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Conformational changes in the antibody constant domains upon hapten-binding
Takuma Sagawa1, Masayuki Oda, Hisayuki Morii
1Research Institute for Biological Sciences (RIBS), Tokyo University of Science, 2669 Yamazaki, Noda, Chiba 278-0022, Japan.
Molecular Immunology
|October 19, 2004
Summary
Hapten-binding to antibodies can induce conformational changes in their Fc regions, as demonstrated by interactions with bacterial proteins A and G. This finding is crucial for understanding antibody structure-function relationships.
Area of Science:
- Immunology
- Structural Biology
- Biochemistry
Background:
- Bacterial proteins A (SpA) and G (SpG) are immunoglobulin receptors.
- These proteins can serve as probes to detect conformational changes in antibody heavy chain constant (C(H)) domains.
Purpose of the Study:
- To investigate whether hapten-binding to antibodies induces conformational changes in their C(H) domains.
- To utilize SpA and SpG as tools to monitor these potential structural alterations.
Main Methods:
- Isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) were employed.
- Interactions between anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibody (Ab) fragments (IgG2a, Fab, F(ab')2) and SpA/SpG were measured.
- Experiments were conducted in the presence and absence of the hapten (NP).
Main Results:
- Hapten-binding weakened the interaction between the F(ab')2 fragment and SpA, suggesting conformational changes in the Fab arms.
- Approximately half of the IgG2a was unable to bind immobilized SpA when the hapten was present.
- Using a mutant SpA, hapten-binding was shown to induce long-range conformational changes in the Fc region of IgG2a.
Conclusions:
- Hapten-binding to antibodies can induce significant conformational changes in both Fab and Fc regions.
- SpA and SpG are valuable tools for detecting these hapten-induced conformational alterations in immunoglobulins.