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Cobra venom factor: structural homology with the third component of human complement.
Journal of Immunology (Baltimore, Md. : 1950)
|December 1, 1984
Summary
Cobra venom factor (CVF) and human complement component 3 (C3) share structural similarities, suggesting CVF evolved from a C3 ancestor protein, not through convergent evolution. This finding impacts our understanding of complement system evolution.
Area of Science:
- Biochemistry
- Immunology
- Evolutionary Biology
Background:
- Cobra venom factor (CVF) activates the complement system, similar to human C3b.
- Understanding the evolutionary relationship between CVF and C3 can provide insights into complement system evolution.
Purpose of the Study:
- To comparatively analyze the structural properties of CVF and human C3 and its cleavage products.
- To determine the evolutionary origin of CVF.
Main Methods:
- Biochemical analyses including amino acid composition, circular dichroism, isoelectric focusing, and immunochemical cross-reactivity.
- Ultrastructural morphology and amino-terminal amino acid sequence analysis were performed.
Main Results:
- CVF and human C3, C3b, and C3c exhibited significant structural similarities.
- CVF showed greater structural resemblance to C3c than to C3b.
- Similarities were observed in amino acid composition, secondary structure, and immunochemical reactivity.
Conclusions:
- CVF is structurally more similar to C3c than C3b.
- CVF is likely derived from a common C3 ancestor protein.
- The findings suggest CVF is not a product of convergent evolution but rather an evolutionary derivative.