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Genetic polymorphism of human C4-binding protein
Journal of Immunology (Baltimore, Md. : 1950)
|September 1, 1983
Summary
Two human complement factor 4-binding protein (C4-bp) forms, A and B, are genetically controlled by a single autosomal locus with at least two codominant alleles. This genetic control influences isoelectric focusing patterns, suggesting a basis for C4-bp variation.
Area of Science:
- Biochemistry
- Human Genetics
- Immunology
Background:
- Complement factor 4-binding protein (C4-bp) is a key regulator of the complement system.
- Previous studies identified distinct electrophoretic forms of C4-bp, but their genetic basis was unclear.
Purpose of the Study:
- To investigate the genetic control and molecular basis of human C4-bp polymorphism.
- To characterize the subunits and allelic variations of C4-bp.
Main Methods:
- Isoelectric focusing (IEF) of neuraminidase-treated plasma samples.
- Affinity chromatography for protein purification.
- Analysis of protein subunits under denaturing conditions.
- Family studies for genetic segregation analysis.
Main Results:
- Two C4-bp forms (A and B) were identified by IEF, exhibiting Mendelian segregation in families.
- C4-bp B consists of two subunits with different isoelectric points, while C4-bp A has only the more basic subunit.
- A single autosomal locus with at least two codominant alleles (C4BP*1 and C4BP*2) controls C4-bp IEF variation.
Conclusions:
- Human C4-bp electrophoretic variation is genetically determined by a single autosomal locus with codominant alleles.
- The identified alleles, C4BP*1 and C4BP*2, code for subunits with distinct isoelectric points.
- The C4BP locus is not closely linked to the HLA or C3 loci.