A fibroin secretion-deficient silkworm mutant, Nd-sD, provides an efficient system for producing recombinant proteins

Satoshi Inoue, Toshio Kanda, Morikazu Imamura, Guo Xing Quan, Katsura Kojima, Hiromitsu Tanaka, Masahiro Tomita, Rika Hino, Katsutoshi Yoshizato, Shigeki Mizuno, Toshiki Tamura

Research output: Contribution to journalArticlepeer-review


The silkworm Nd-sD mutant is silk fibroin-secretion deficient. In the mutant, a disulfide linkage between the heavy (H) and light (L) chains, which is essential for the intracellular transport and secretion of fibroin, is not formed because of a partial deletion of the L-chain gene. To utilize the inactivity of the mutant L-chain, we investigated the possibility of using the Nd-sD mutant for the efficient production of recombinant proteins in the silkworm. A germ line transformation of the mutant with a normal L-chain-GFP fusion gene was performed. In the transgenic mutant, normal development of the posterior silk gland (PSG) was restored and it formed a normal cocoon. The biochemical analysis showed that the transgenic silkworms expressed the introduced gene in PSG cells, produced a large amount of the recombinant protein, secreted it into the PSG lumen, and used it to construct the cocoon. The molar ratio of silk proteins, H-chain:L-chain-GFP:fibrohexamerin, in the lumen and cocoon in the transgenic silkworm was 6:6:1, and the final product of the fusion gene formed about 10% of the cocoon silk. This indicates that the transgenic mutant silkworm possesses the capacity to produce and secrete the recombinant proteins in a molar ratio equal to that of the fibroin H-chain, contributing around half molecules of the total PSG silk proteins.

Original languageEnglish
Pages (from-to)51-59
Number of pages9
JournalInsect Biochemistry and Molecular Biology
Issue number1
Publication statusPublished - 2005 Jan
Externally publishedYes


  • Bioreactor
  • Bombyx
  • Fibroin
  • Intracellular transport
  • Nd-s mutant
  • PiggyBac
  • Recombinant protein
  • Silkworm
  • Transgenic

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Insect Science


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