Plasmic degradation products of human fibrinogen II. Chemical and immunological relation between fragment E and N-DSK

Abstract

The relation between Fragment E and N-DSK was studied by immunological and chemical techniques. Fragment E was shown to have antigenic determinants in common with N-DSK. Cleavage of Fragment E with cyanogen bromide produced one main fragment (“E-knot”), reacting with anti N-DSK serum and having a molecular weight of 43 000. On thrombic digestion this fragment, like Fragment E, released Fibrinopeptide A. “E-knot” had the same content of disulphide bridges and neutral sugars as Fragment E and N-DSK. Tryptic peptides of “E-knot” were separated by two dimensional thin layer electrophoresis-chromatography. Subsequently the peptides were subjected to amino acid analysis and the amino acid compositions compared with those of tryptic peptides of N-DSK. Our results show that “E-knot” is part of N-DSK and most molecules satisfy the formula: (A α 1 Ala-51Met, β54Lys-115Met, γ1 Tyr-58Lys) 2. Some molecules appear to be lacking one or more of the following structural features: Aα1Ala-16Arg, Aα51Met, β54Lys, β54Lys-58Lys and γ54Thr-58Lys. In addition to these specified structures Fragment E contains sequences extending beyond Aα51Met and Bβ115Met.