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Functional and structural characterisation of human colostrum free secretory component
Adel Almogren1, Alexandra Bonner, Stephen J Perkins
1Department of Pathology, College of Medicine and King Khalid University Hospital, King Saud University, P.O. Box 2925, Riyadh 11461, Saudi Arabia.
Molecular Immunology
|February 24, 2009
Summary
Free secretory component (FSC) is slightly smaller than bound SC, indicating variable cleavage sites on the polymeric Ig receptor. This structural difference does not affect FSC
Area of Science:
- Immunology
- Molecular Biology
- Structural Biology
Background:
- Secretory component (SC) and secretory IgA (SIgA) are crucial for mucosal immunity.
- Free secretory component (FSC) possesses innate neutralizing properties.
- The production mechanism of SC and FSC via polymeric Ig receptor cleavage is not fully understood.
Purpose of the Study:
- To investigate the structural differences between FSC and SIgA-bound SC.
- To characterize the functional activity and solution structure of FSC.
- To elucidate the cleavage sites of the polymeric Ig receptor.
Main Methods:
- SDS-PAGE analysis to compare molecular sizes.
- Functional assays to assess FSC binding and activity.
- Analytical ultracentrifugation and X-ray scattering to determine solution structure.
Main Results:
- FSC is slightly smaller than SIgA-bound SC, suggesting variable cleavage.
- FSC retains functional activity, binding IgA and activating eosinophils.
- FSC from different secretions exhibits varying molecular sizes.
- Solution structure analysis reveals a compact, J-shaped conformation for FSC.
Conclusions:
- Variable C-terminal cleavage of the polymeric Ig receptor produces FSC.
- The C-terminal linker's cleavage does not impact FSC's known functions.
- Structural variations in FSC may arise from the absence of dimeric IgA during cleavage.
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