Amino acid sequence of a polymorphic segment from fragment C4d of human complement component C4
FEBS Letters
|April 18, 1983
Summary
Researchers determined the amino acid sequence of a human complement C4d segment, identifying genetic variations. These findings help explain inherited differences in complement C4 observed through gel electrophoresis.
Area of Science:
- Biochemistry
- Immunology
- Genetics
Background:
- Human complement component C4 (C4) exists in electrophoretically distinct genetic variants.
- Understanding the molecular basis of these variants is crucial for immunology and diagnostics.
Purpose of the Study:
- To determine the amino acid sequence of a 106-residue segment of human complement C4d.
- To identify and characterize sequence polymorphisms within this C4d segment.
- To correlate observed sequence variations with inherited C4 variants.
Main Methods:
- Automated amino acid sequence analysis.
- Fragment generation via CNBr cleavage.
- Enzymatic digestion using trypsin.
Main Results:
- The amino acid sequence of a 106-residue C4d segment was elucidated.
- Polymorphism was detected at three positions (residues 9, 12, and 102).
- Variations include specific amino acid substitutions (e.g., Val/Leu, Ala/Arg, Val/Arg) and a Ser/Ala difference at position 98 when compared to nucleic acid sequence data.
Conclusions:
- The determined C4d sequence and identified polymorphisms provide molecular insights into human C4 heterogeneity.
- These findings contribute to explaining the basis of inherited C4 variants observed in gel electrophoresis studies.
- The study highlights the utility of protein sequencing in understanding genetic variations in complement proteins.
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