Analysis of C3b/C4b receptor (CR1) polymorphic variants by tryptic peptide mapping
Molecular Immunology
|June 1, 1986
Summary
The human C3b/C4b receptor (CR1) exhibits allelic variation due to repeating amino acid sequences, not significant amino acid differences between variants. This structural conservation explains the receptor
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- The human C3b/C4b receptor (CR1) is a key glycoprotein in complement system regulation.
- CR1 is expressed on peripheral blood cells and exists in four codominant allelic variants based on molecular weight (160,000–250,000 Da).
Purpose of the Study:
- To investigate the structural basis of CR1 allelic polymorphism.
- To compare the amino acid sequences of different CR1 variants.
Main Methods:
- Purification of CR1 from erythrocytes of donors expressing three allelic variants using iC3-Sepharose affinity chromatography.
- Surface labeling with 125I and comparison of variants via tryptic peptide mapping (TPM).
- Comparison of CR1 from erythrocytes and granulocytes from the same donor.
Main Results:
- Tryptic peptide maps of the CR1 variants were nearly identical, indicating high conservation of amino acid sequences.
- TPMs of CR1 purified before or after iodination were similar.
- Minor differences were observed between erythrocyte and granulocyte CR1, suggesting potential post-translational modifications or expression differences.
Conclusions:
- The allelic variation in CR1 molecular weight is likely due to differences in the number of repeating amino acid sequences within the protein.
- The core amino acid sequence of CR1 is highly conserved across different allelic variants.
