Katsura Kojima

Learn More
We constructed a new plasmid vector for the production of a modified silk fibroin heavy chain protein (H-chain) in the transgenic silkworm. The plasmid (pHC-null) contained the promoter and the 3' region of a gene encoding the H-chain and the coding regions for the N-terminal domain and the C-terminal domain of the H-chain. For the model protein, we cloned(More)
Silk fibroin of Bombyx mori is secreted from the posterior silk gland (PSG) as a 2.3-MDa elementary unit, consisting of six sets of a disulfide-linked heavy chain (H-chain)-light chain (L-chain) heterodimer and one molecule of fibrohexamerin (fhx)/P25. Fhx/P25, a glycoprotein, associates noncovalently with the H-L heterodimers. The elementary unit was found(More)
Regenerated silk fibroin fibers from the cocoons of silkworm, Bombyx mori, were prepared with hexafluoro solvents, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) or hexafluoroacetone-trihydrate (HFA), as dope solvents and methanol as coagulation solvent. The regenerated fiber prepared from the HFIP solution showed slightly larger tensile strength when the draw(More)
Spider dragline silk is a natural fiber that has excellent tensile properties; however, it is difficult to produce artificially as a long, strong fiber. Here, the spider (Araneus ventricosus) dragline protein gene was cloned and a transgenic silkworm was generated, that expressed the fusion protein of the fibroin heavy chain and spider dragline protein in(More)
A binary gene expression system using the yeast GAL4 DNA-binding protein and the upstream activating sequence (UAS) of galactose-driven yeast genes is an established and powerful tool for the analysis of gene function. However, in the domesticated silkworm, Bombyx mori, this system has been limited in its utility by the relatively low transcriptional(More)
Silk production is integral to the construction of nests or cocoons for many Aculeata, stinging Hymenopterans such as ants, bees and wasps. Here we report the sequences of new aculeate silk proteins and compare cross-linking among nine native silks from three bee species (Apis mellifera, Bombus terrestris and Megachile rotundata), three ant species(More)
Complete amino acid sequences of the four major proteins (Vssilk 1-4) of silk (hornet silk) obtained from yellow hornet ( Vespa simillima , Vespinae, Vespidae) cocoons have been determined. The native structure of the hornet silk (HS), in which Vssilk 1-4 have an alpha-helix domain with coiled-coil alpha-helices and a beta-sheet domain, is restored when(More)
Double-strand breaks (DSBs) are potentially lethal lesions causing the loss of chromosomal information. Eukaryotic cells have evolved the error-free repair systems of DSBs by homologous recombination (HR) through gene conversion with or without crossing over. In this study, we have developed a rapid assay system for extrachromosomal HR events in the(More)
The silkworm Nd-s(D) 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(More)
Bombyx mori (silkworm) silk proteins are being utilized as unique biomaterials for medical applications. Chemical modification or post-conjugation of bioactive ligands expand the applicability of silk proteins; however, the processes are elaborate and costly. In this study, we used transgenic silkworm technology to develop single-chain variable fragment(More)