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Structural evidence that complement factor B constitutes a novel class of serine protease
The Journal of Biological Chemistry
|September 25, 1980
Summary
Complement factor B, a protein involved in the immune system, has been identified as a serine protease. This discovery reveals new insights into its enzymatic activity and potential roles in biological processes.
Area of Science:
- Biochemistry
- Immunology
- Proteomics
Background:
- Complement factor B is a key component of the complement system, a crucial part of innate immunity.
- The precise enzymatic nature and classification of complement factor B have been subjects of ongoing research.
Purpose of the Study:
- To elucidate the enzymatic properties of complement factor B.
- To determine if complement factor B possesses serine protease activity.
Main Methods:
- Isolation and characterization of cyanogen bromide peptides from complement factor B.
- Automated amino acid sequencing of isolated peptides (CB2-3 and CB2-2).
- Mild acid hydrolysis to fragment larger peptides and identify active site sequences.
Main Results:
- The COOH-terminal peptide of complement factor B (28,000 daltons) was isolated.
- Amino acid sequencing revealed homology to known serine proteases, including the active site sequence Ala-Ala-His-Cys in peptide CB2-2.
- A distinct 8,000-dalton fragment contained the active site serine sequence Gly-Asp-Ser-Gly-Gly-Pro.
Conclusions:
- Complement factor B is definitively identified as a serine protease.
- While possessing serine protease activity, its activation mechanism differs from other enzymes in this class.
- This finding expands the understanding of complement system enzymology.