Related Experiment Videos
CNBr cleavage of the light chain of human complement factor I and alignment of the fragments
Insights
Researchers purified human complement Factor I and analyzed its light chain. Sequence analysis identified active-site residues and potential glycosylation sites, advancing understanding of this complement system protein.
Area of Science:
- Biochemistry
- Immunology
- Proteomics
Background:
- Human complement Factor I is a critical serine protease regulating the complement system.
- Understanding its structure and function is essential for comprehending immune responses and developing therapeutics.
Purpose of the Study:
- To elucidate the primary structure of the human complement Factor I light chain.
- To identify key functional regions, including the active site and potential glycosylation sites.
Main Methods:
- Purification of human complement Factor I light and heavy chains using high-pressure gel-permeation chromatography.
- Cyanogen bromide (CNBr) cleavage of the light chain and purification of resulting fragments via gel filtration.
- N-terminal sequence analysis and peptide mapping (arginine cleavage) for sequence determination and alignment.
Main Results:
- Successfully purified the light and heavy chains of human complement Factor I.
- Generated and purified four major fragments from CNBr cleavage of the light chain.
- Determined the N-terminal sequence of approximately 200 of the 240 amino acid residues of the light chain.
- Proposed an alignment based on sequence homology with other serine proteases.
- Identified the active-site serine residue and three potential sites for carbohydrate attachment.
Conclusions:
- The primary structure of the human complement Factor I light chain has been significantly elucidated.
- Key functional sites, including the active serine and potential glycosylation sites, have been identified.
- This detailed sequence information provides a foundation for further functional studies of complement Factor I.
Abstract:
The light chain and heavy chain of reduced and alkylated human complement Factor I were purified by high-pressure gel-permeation chromatography. CNBr cleavage of Factor I light chain yielded four major fragments, which were purified by gel filtration. N-Terminal sequence analysis of the CNBr-cleavage fragments allowed identification of 200 of the approx. 240 amino acid residues of the light chain. An alignment is proposed, based on sequence analysis of peptides obtained after cleavage at arginine residues of the light chain and on homology of the sequence determined with that of other serine proteinases. The sequence around the active-site serine residue was established and three potential attachment sites for carbohydrate moieties were identified.