On the Primary Structure of the A Chains

Abstract

During plasma digestion of fibrinogen a degradation product with molecular weight (MW) of about 50,000 appear very early in the digest. As revealed by sodium dodecyl sulphate (SDS) gel electrophoresis this product has its origin in the A chain. Upon further hydrolysis the 50,000 MW fragment is degraded to a 25,000 MW fragment. Both the 50,000 and 25,000 MW fragments have been isolated. After treatment with cyanogenbromide (CNBr) of the 50,000 MW fragment and separation of the peptides obtained, a fragment with MW of 30,000 and two fragments of smaller MW were isolated. As revealed by amino acid sequence analysis and peptide mapping the 30,000 MW fragment was identical to a hydrophilic sulfurcontaining peptide (Hi2-DSK), isolated after CNBr-treatment of the whole fibrinogen molecule. The amino acid sequence analysis of the fragments is in progress. Amino acid sequences analysis of the 25,000 MW fragment gave the following sequence: Ala-Len-Thr- Asp-Met-Pro- Gln-Met- Arg-Met-Glu-Leu-Glu-. From residue number 11 it appears to be identical to the Hi2-DSK fragment. However, the 25,000 MW fragment is shorter at the COOH-terminal end.