| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The results obtained in this study are as follows;
1. Effect of lipid composition for binding of ricin A- and B-chains to lipid bilayer isolated A- and B-chains bound to the liposomes consisting of various lipid compositions in the presence and absence of salt, indicating a participation of the hydrophobic interaction for the binding of ricin A- and B-chains to lipid bilayer. These bindings decreased remerkably in the liposomes containing over 10% of cholesterol.
2. Cytotoxicity of the hybrid molecules of ribosome-inactivating protein/B-chain hybrid molecules were prepared by cross-linking two ribosome-inactivating proteins having no surface hydrophobicity to ricin B-chain with SPDP, and examined their cyto-toxicity toward Hela cells. No toxicity of these hybrid molecules suggested an impor-ance of the A-chain structure including surface hydrophobicity for transmembrane of the ricin molecule.
3. Hydrophobicities of ricin and its subunits. From the results obtained by fluorometric method using cis-parnaric acid and by binding with Triton X-100, it was revealed that the A-chain had about 4 times larger hydrophobic regions on its molecular surface than the B-chain, and these surface hydrophobic regions were masked in the ricin molecule.
4. DPPC-liposome-binding/insertion site of ricin A- and B-chains. From the trypsin treated a-chain-liposome complex, four peptides starting from Ile-1, Phe-57, Glu-135 or Phe-181 were obtained. Since the tryptic peptides Phe-57 - Arg-85 and Glu-135 - Arg-166 bound to liposomes, it was inferred that the lipo-some binding/insertion site of ricin A-chain may be C-terminal domain including Gly-35 - Asn-47 region.
Main peptide remained in the B-chain-liposome complex after subtilisin digestion was identified to be Ala-1 - Asn-46. From this result, it was concluded that the liposome-binding/insertion site of ricin B-chain is N-terminal region of the B-chain.
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