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The structure of bovine secretory component.
1Agricultural and Food Research Council, Institute of Animal Physiology and Genetic Research, Babraham, Cambridge, U.K.
Veterinary Immunology and Immunopathology
|December 1, 1987
Summary
Bovine secretory component (SC) is the extracellular part of an epithelial receptor involved in IgA dimer transport. Its structure consists of five immunoglobulin-like domains, with the first three crucial for binding.
Area of Science:
- Immunology
- Biochemistry
- Structural Biology
Background:
- Secretory component (SC) plays a role in immunoglobulin transport.
- Understanding the structure and function of bovine SC is crucial for elucidating mucosal immunity mechanisms.
Purpose of the Study:
- To determine the structure and function of bovine secretory component (SC).
- To investigate the role of SC in the transport of IgA dimers.
Main Methods:
- Tryptic digestion of bovine SC to yield fragments.
- N-terminal amino acid sequencing of SC fragments.
- Isolation and characterization of a membrane-bound protein.
- Computerized prediction and modeling for structural analysis.
Main Results:
- Bovine SC is a single glycosylated polypeptide chain with five immunoglobulin-like domains.
- A membrane protein (Mr 94,000) binds J-chain linked IgM and IgA dimers and cleaves into SC-like and hydrophobic portions.
- SC mediates IgA dimer transport to mucosal surfaces.
- Domains 1-3 of SC are primarily involved in binding IgA and IgM dimers.
Conclusions:
- Bovine SC is the extracellular portion of an epithelial receptor facilitating IgA dimer transport.
- The structure of SC is an elongated "zig-zag" conformation.
- Specific domains within SC are responsible for differential binding affinities to IgA and IgM dimers.