The Occurrence of Small Component Proteins in the Cocoon Fibroin of Bombyx mori

Abstract

Small component proteins were isolated from cocoons of Bombyx mori and assayed for amino acid composition and molecular size. The main fraction of the small components was demonstrated to possess the same characteristics as that of the small component isolated from posterior silk gland fibroin. The small component of cocoon was also shown to be connected to the large component of cocoon fibroin with disulfide bonds. The ratio of the small component to the large component was about one to one in molar ratio. Thus, we can conclude that cocoon fibroin is composed of each one mole of large and small subunits.