CNBr cleavage of the light chain of human complement factor I and alignment of the fragments.

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.