Some amino acid sequences in the amorphous fraction of the fibroin of Bombyx mori

Abstract

When the precipitate formed by the action of chymotrypsin on an aqueous solution of silk fibroin has been removed, the liquor remaining consists of a solution of peptides having a mean chain length of about 8. Separation of these peptides by ion-exchange chromatography yields about 20 fractions, most of which are small; 2 of the 4 main fractions account for 39.8% of the total molar yield of peptides. One of these 2 fractions consists of 2 octapeptides. Gly-Ala-Gly-Ala-Gly-Ala-Gly-Tyr and Gly-(Gly3,Ala2,Val)-Tyr, and the other is the tetrapeptide Gly-Ala-Gly-Tyr. The molar ratios in which these 3 peptides occur in the liquor is 44:3 respectively, and their relevance to the structure of the fibroin molecule is discussed.