Immunological identification of the major disulfide-linked light component of silk fibroin

The light protein components of silk fibroin were analyzed by Western blotting using polyclonal antibodies against two synthetic peptides that are segment of the light (L-) chain [Yamaguchi et al. (1989) J. Mol. Biol. 210, 127-139] and P25 [Chevillard et al. (1986) Sericologia 26, 435-449], respectively, and against the whole L-chain. Both the L-chain and P25 were present with fibroin in the lumen of the posterior silk gland and in the cocoon. The L-chain was identified as the major light component that was disulfide-linked to the fibroin heavy (H-) chain, whereas P25 was a minor component whose association with the H-chain was suggested to be non-covalent.